The Project Gutenberg eBook of Natural Gemstones

This ebook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this ebook or online at www.gutenberg.org. If you are not located in the United States, you will have to check the laws of the country where you are located before using this eBook.

Title: Natural Gemstones

Author: Geological Survey

Release date: January 16, 2015 [eBook #47999]

Most recently updated: October 24, 2024

Language: English

Credits: Produced by Stephen Hutcheson, Dave Morgan, Carol Spears

and the Online Distributed Proofreading Team at

http://www.pgdp.net

*** START OF THE PROJECT GUTENBERG EBOOK NATURAL GEMSTONES ***

Quartz, Rhode Island.

Amethyst crystals, Mexico.

U.S. Department of the Interior

U.S. Geological Survey

Natural

Gemstones

Searching for gemstones in the United States is a popular recreational activity for collectors and hobbyists

Natural gemstones

A natural gemstone is a mineral, stone, or organic matter that can be cut and polished or otherwise treated for use as jewelry or other ornament. A precious gemstone has beauty, durability, and rarity, whereas a semiprecious gemstone has only one or two of these qualities. A gem is a gemstone that has been cut and polished.

Diamond, corundum (ruby and sapphire), beryl (emerald and aquamarine), topaz, and opal are generally classed as precious stones. All other gemstones are usually classed as semiprecious.

A mineral is any naturally formed homogeneous inorganic material.

A mineralogist is a person who studies the formation, occurrence, properties, composition, and classification of minerals.

A gemologist is a person who has successfully completed recognized courses in gemology (the science and study of gemstones) and has proven skills in identifying and evaluating gem materials.

A lapidary is a cutter, polisher, or engraver of precious stones.

Geologic environment

Gemstones are not plentiful. Gemstones do not form “ore” deposits in the normal sense.

Gems, when present at all, tend to be scattered sparsely throughout a large body of rock or to have crystallized as small aggregates or fill veins and small cavities.

Even stream gravel concentrations tend to be small—a few stones in each of several bedrock cracks, potholes, or gravel lenses in a stream bed.

The average grade of the richest diamond kimberlite pipes in Africa is about 1 part diamond in 40 million parts “ore.” Kimberlite, a plutonic igneous rock, ascends from a depth of at least 100 kilometers (60 miles) to form a diatreme (narrow cone-shaped rock body or “pipe”). Moreover, because much diamond is not of gem quality, the average stone in an engagement ring is the product of the removal and processing of 200 to 400 million times its volume of rock.

Gemstones occur in most major geologic environments.

Each environment tends to have a characteristic suite of gem materials, but many kinds of gems occur in more than one environment. Most gemstones are found in igneous rocks and alluvial gravels, but sedimentary and metamorphic rocks may also contain gem materials.

Examples of geologic environments in which gemstones are found:

Pegmatite—a coarse-grained intrusive igneous rock body, occurring as dikes (a tabular-shaped body), lenses, or veins in the surrounding rock.

Stream gravels (placers)—deposits of heavier and more durable than average minerals that have been eroded out of the original rock. Often tourmaline, beryl, and many other gem-quality minerals have eroded out of the original rock in which they formed and have moved and been concentrated locally by water in streams. Sapphires in Judith Basin County, Montana, were first found when the gravels were worked for gold from 1895 to 1930.

Metamorphic rocks—rocks that have been altered by great heat, pressure, or both. Garnet, for example, is commonly found as crystals in gneiss and mica schist.

Quartz with phantoms, Brazil.

Aquamarine, Brazil.

Mineral gemstones

Hardness and specific gravity are two of the major characteristics of gemstones.

Hardness of a gemstone is its resistance to scratching and may be described relative to a standard scale of 10 minerals known as the Mohs scale. F. Mohs, an Austrian mineralogist, developed this scale in 1822.

According to Mohs’ scale, the hardness of—

Talc is

1

Gypsum is

2

Calcite is

3

Fluorite is

4

Apatite is

5

Feldspar is

6

Quartz is

7

Topaz is

8

Sapphire is

9

Diamond is

10

Specific gravity is the number of times heavier a gemstone of any volume is than an equal volume of water; in other words, it is the ratio of the density of the gemstone to the density of water.

The 16 mineral gemstone groups listed below are highly prized for their beauty, durability, and rarity:

Beryl (hardness: 7.5-8 Mohs)

Beryllium aluminum silicate

Specific gravity: 2.63-2.91

Emerald: Intense green or bluish green

Aquamarine: Greenish blue or light blue

Morganite: Pink, purple pink, or peach

Heliodore: Golden yellow to golden green

Red beryl: Raspberry red

Goshenite: Colorless, greenish yellow, yellow green, brownish

Chrysoberyl (hardness: 8.5 Mohs)

Beryllium aluminum oxide

Specific gravity: 3.68-3.78

Chrysoberyl: transparent yellowish green to greenish yellow and pale brown

Alexandrite: red in incandescent light and green in daylight

Cat’s eye: usually yellowish or greenish

Corundum (hardness: 9 Mohs)

Aluminum oxide

Specific gravity: 3.96-4.05

Ruby: Intense red

Sapphire: Blue

Diamond (hardness: 10 Mohs)

Carbon

Specific gravity: 3.51

Colorless to faint yellowish tinge, also variable

Feldspar (hardness: 6-6.5 Mohs)

Two distinctly different alkali alumino silicates: the Plagioclase and the Alkali Feldspar Series

Specific gravity: 2.55-2.76

Plagioclase Series—

Labradorite: Colorful, iridescent, also transparent stones in yellow, orange, red, and green

Sunstone: Gold spangles from inclusions of hematite

Peristerite: Blue white iridescence

Alkali Feldspar Group—

Orthoclase: Pale yellow, flesh red

Amazonite: Yellow green to greenish blue

Moonstone: Colorless; also white to yellowish, and reddish to bluish gray

Garnet (hardness: 6.5-7.5 Mohs)

A group of silicate minerals

Specific gravity: 3.5-4.3

Almandine: Orangy red to purplish red

Almandine-spessartine: Reddish orange

Andradite: Yellowish green to orangy yellow to black

Demantoid: Green to yellow green andradite

Topazolite: Yellow to orangy yellow

Grossular: Colorless; also orange, pink, yellow, and brown

Tsavorite: Green to yellowish green

Hessonite: Yellow orange to red

Pyrope: Colorless; also pink to red

Chrome pyrope: Orange red

Pyrope-Almadine: Reddish orange to red purple

Pyrope-Spessartine: Greenish yellow to purple

Malaia: Yellowish to reddish orange to brown

Color-change garnet: Blue green in daylight to purple red in incandescent light

Rhodolite: Purplish red to red purple

Spessartine: Yellowish orange

Uvarovite: Emerald green

Jade (hardness: 6 Mohs)

Nephrite

Calcium magnesium silicate

Specific gravity: 2.9-3.1

White, deep green, creamy brown

Jadeite

Sodium aluminum silicate

Specific gravity: 3.1-3.5

White, leafy and blue green, emerald green, lavender, dark blue green and greenish black, deep emerald-green

Lapis lazuli (hardness: 5-5.5 Mohs)

A rock composed mainly of the mineral lazurite with variable amounts of pyrite (brassy flecks) and white calcite

Specific gravity: 2.7-2.9

Diamond Star of Sierra Leone.

Deep blue, azure blue, greenish blue (bluish color with flecks of white and gold)

Opal (hardness: 5.5-6.5 Mohs)

Hydrated silica

Specific gravity: 1.98-2.25

White opal: Opaque, porcelain-like white material; colors resemble flashes or speckles

Black opal: Flashes and speckles appear against black background

Water opal: A transparent, colorless opal is the background for brilliant flashes of color

Fire opal: Reddish or orange opal

Peridot [Olivine] (hardness: 7 Mohs)

Magnesium iron silicate

Specific gravity: 3.22-3.45

Olive to lime green

Quartz (hardness: 7 Mohs)

Silicon dioxide or silica

Specific gravity: 2.65

Coarsely crystalline varieties of silica—

Rock crystal: Colorless

Amethyst: Purple

Citrine: Yellow to amber

Morion: Black

Smoky quartz or cairngorm: smoky gray to brown

Rose quartz: Translucent pink

Green quartz or praziolite: Green

Cryptocrystalline varieties of silica—

Chalcedony and Jasper (variable)

Agate: Bull’s eye agate, Iris or fire agate, Onyx, Sardonyx.

Bloodstone or heliotrope. Carnelian. Chrysoprase. Moss agate. Plasma. Prase. Sard. Jasper.

Spinel (hardness: 8 Mohs)

Magnesium aluminum oxide

Specific gravity: 3.58-4.06

Balas ruby: Red

Almandine spinel: Purple red

Rubicelle: Orange

Sapphire spinel and ghanospinel: Blue

Chlorspinel: Green

Candelabra: white quartz, blue-capped red elbaite, and tan albite, California.

Topaz (hardness: 8 Mohs)

Aluminum silicate fluoride hydroxide

Specific gravity: 3.5-3.6

Wine yellow, pale blue, green, violet, or red

Tourmaline (hardness: 7-7.5 Mohs)

Complex aluminum borosilicate (Elbaite, Dravite, Uvite)

Specific gravity: 3.03-3.25

Achorite: Colorless

Brazilian emerald: Green

Dravite: Brown

Indicolite: Dark blue

Rubellite: Pink to red

Siberite: Violet

Verdilite: Green

Turquoise (hardness: 5-6 Mohs)

Hydrous copper aluminum phosphate

Specific gravity: 2.6-2.8

Sky blue; greenish blue

Zircon (hardness: 7.5 Mohs)

Zirconium silicate

Specific gravity: 4.6-4.7

Jargon: Variable

Matura diamond: Colorless

Hyacinth: Yellow, orange, red, brown

The Hooker Emerald, Colombia.

Birthstones

Month of birth

Gemstone

Color

January

Garnet

Dark red

February

Amethyst (Quartz)

Purple

March

Aquamarine (Beryl) or Bloodstone (Quartz)

Pale blue

April

Diamond or Rock Crystal (Quartz)

Colorless

May

Emerald (Beryl)

Bright green

or Chrysoprase (Quartz)

Pale green

June

Pearl or Moonstone (Feldspar)

Cream

July

Ruby (Corundum) or Carnelian (Quartz)

Red

August

Peridot

Pale green

or Sardonyx (Quartz)

Brown and white

September

Sapphire (Corundum)

Pale to dark blue

or Lapis Lazuli

Deep blue

October

Opal or Tourmaline

Variegated

November

Topaz or Citrine (Quartz)

Yellow

December

Turquoise

Sky blue

Organic gemstones

The four organic gemstone groups listed below are highly prized for their beauty and rarity. However, they are not as durable as gemstones from minerals:

Amber (hardness: 2-2.5 Mohs)

A mixture of hydrocarbons

Specific gravity: 1.05-1.096

Hard fossil resin or sap of ancient pine trees. Usually amorphous (lacks crystalline structure). Sometimes mined, sometimes gathered on seashores.

Varies from transparent to semitransparent and generally from light yellow to dark brown, but can be orange, red, whitish, greenish-brown, blue, or violet. Can be dyed in any color.

Takes a fine polish. Used mainly in making beads or other ornaments.

Coral (hardness: 3.5-4 Mohs)

Formed mainly of calcite (calcium carbonate) or conchiolin, a horny organic substance

Specific gravity: 2.60-2.70

Each coral polyp, a tiny marine animal that lives in enormous colonies, extracts calcium carbonate from the sea and exudes it to build a protective home around and above itself. Each generation of polyps dies in its protective home and each succeeding generation builds on top of its predecessor.

Gem coral ranges from semitranslucent to opaque and occurs in white, pink, orange, red, blue, violet, golden, and black. The black and golden corals are largely horny organic substances, not calcium carbonate.

The finest coral is used to make figurines, cameos, carvings, and beads.

Jet (hardness: 2.5-4 Mohs)

Carbon plus various hydrocarbon compounds

Specific gravity: 1.30-1.32

This compact velvet-black coal takes a good polish and is often cut into beads, bracelets, and a wide range of decorative and useful objects.

Pearl (hardness: 2.5-4.5 Mohs)

Formed within a mollusk, such as an oyster, that deposits a substance called nacre around an irritant that entered the organism

Specific gravity: 2.71

Pearl-bearing mollusks are found in both salt and fresh water. Salt-water pearls of gem quality are usually preferred for jewelry; they are produced almost entirely by the mollusk Pinctada. Fresh-water pearls are produced by various clams and mussels.

Natural pearls come in various shapes: round, pear, drop, egg, and others. They also come in various colors, such as white, cream, light rose, cream rose, black, gray, bronze, blue, dark blue, blue green, red, purple, yellow, and violet.

Buyer beware

Inexperienced buyers must take whatever steps are needed to ensure that gems they intend to purchase are exactly what the seller purports them to be and that they are being offered at a fair market price.

More and more synthetic gems—and inferior grades and cuts of natural gems—are being sold to unwary buyers by unscrupulous sellers.

Since 1935, the mining of gemstones in the United States has been almost entirely a recreational activity of mineral collectors and hobbyists.

In recent years, very few individuals have derived their entire income from gemstones mined by themselves.

This is not to say that the proprietors of roadside rock shops buy all of their stock from others. Rock shops are abundant in areas of the United States that are rich in gem materials, and the shops tend to specialize in the local gem commodities, most of which the proprietors gather.

Rather than doing the mining themselves, owners of land that has a deposit of gem-quality minerals sometimes charge hobbyists for the right to collect gemstones. For example, diamond in Arkansas, opal in Idaho, and agate in Oregon and Washington are mined by hobbyists under this “fee digging” arrangement.

However, the flow of money into the local economy by paying these small fees and by the purchase of gemstones is minor compared to the money the enthusiasts spend for lodging and other living expenses while visiting an area to dig for gemstones.

Several kinds of natural gemstones have been found in every State of the United States, but much larger deposits of the most precious kinds are found outside the United States.

The 1990 U.S. output of natural gemstones was primarily from Tennessee, California, Arizona, Arkansas, Montana, Nevada, and Maine.

An estimated 80,000 visitors found a total of 315 carats of diamonds in the Crater of Diamonds State Park in Arkansas. There were sizeable yields of freshwater pearls in Tennessee, turquoise in Arizona and Nevada, tourmaline in Maine, and tourmaline, kunzite, and garnet in California.

Gemstones: Value of U.S. production vs. imports, 1986 and 1989[1]

Production

1986

1989

Natural

$9.3

million

$43.0

million[2]

Synthetic

10.3

23.5

$19.6

$66.5

Mine employment

300

800

Imports for consumption:

$4.18

billion

$5.00

billion

Apparent reliance on imports over exports[3]

99%

98%

[1]Estimated.

[2]Including freshwater pearls natural, and cultured.

[3]Imports - exports + adjustments for Government and industry stock changes. Source: Mineral Commodity Summaries, 1991, U.S. Bureau of Mines.

U.S. production of commercial gems includes agate, beryl, freshwater pearl, garnet, jade, jasper, mother-of-pearl, opal, peridot, quartz, sapphire, tourmaline, and turquoise.

Except for the few gem diamonds found each year in Arkansas, U.S. diamond production is very low.

Yet exploration for diamonds continues in Alaska, Colorado, Michigan, Minnesota, Wisconsin, and Wyoming. A diamond mining project at the Crater of Diamonds State Park in Arkansas is still being evaluated by the State.

World diamond reserves are estimated to be about 300 million carats, including near-gem materials but not diamonds of abrasive quality.

Most of the reserves are in southern Africa, Siberia, and western Australia. It is difficult to estimate reserves because the value of a given deposit varies with the market for the gems.

Jade nephrite, China.

The Hope Diamond, India.

Chemical formulas of gemstones

Beryl

Be_3Al_2Si_6O_1_8

Chrysoberyl

BeAl_2O_4

Coral

CaCO_3

Corundum

Al_2O_3

Diamond

C

Feldspar

Plagioclase Series:

(Na,Ca)Al(Al,Si)Si_2O_8

Alkali Feldspar Group:

Mixtures of Orthoclase—KAlSi_3O_8 and Albite—NaAlSi_3O_8

Garnet

Almadine—Fe_3Al_2(SiO_4)3

Andradite—Ca_3Fe_2(SiO_4)3

Grossular—Ca_3Al_2(SiO_4)3

Pyrope—Mg_3Al_2(SiO_4)3

Spessartine—Mn_3Al_2(SiO_4)3

Uvarovite—Ca_3Cr_2(SiO_4)3

Jade

Nephrite—Ca_2(Mg,Fe)5(Si_8O_2_2) (OH)2

Jadeite—NaAl(Si_2O_6)

Lapis lazuli

Lazurite—(Na,Ca)8(AlSiO_4)6 (SO_4,S,Cl)2

Opal

Hydrated Silica—SiO_2·nH_2O

Peridot

(Mg,Fe)2(SiO_4)

Quartz

SiO_2

Spinel

MgAl_2O_4

Topaz

Al_2SiO_4(F,OH)2

Tourmaline

XY_3Al_6(BO_3)3(Si_6O_1_8) (OH_4)

[X is usually Na but may be replaced by Ca; Y is one of several metal ions]

Turquoise

CuAl_6(PO_4)4(OH)8·4H_2O

Zircon

ZrSiO_4

Some ways to contact a local rock, mineral, or gem club

If you have access to the most recent April Buyer’s Guide issue of the Lapidary Journal magazine, scan its lists of gem and mineral clubs in the United States and other countries. (The address of the Lapidary Journal is given in the list of journals cited below.)

Talk to a member of the geology or earth science department of your local college or university.

Talk to a member of the science department of your local high school.

Write to the—

Eastern Federation of Mineralogical and Lapidary Societies

Box 10119

Alexandria, VA 22310-0119

or the

Midwest Federation of Mineralogical and Geological Societies

306 Somonauk

Park Forest, IL 60466

Check the phone book for your nearest rock and mineral shop and talk to the owners.

Role of the U.S. Geological Survey (USGS)

The USGS reports deposits that seem likely to contain gemstones. It is not a function of the USGS to exploit such resources.

USGS geologists perform continuing research on kimberlites, the initial source of diamonds. Not all kimberlites are diamond-bearing, and some of the research is directed to learning what indications you look for during exploration to distinguish fertile from barren kimberlite. USGS geologists are compiling a U.S. map showing the locations of known kimberlites.

Selected general references

A trip to your local library is the best first step toward understanding gemstones and toward planning a trip to gem and rock shops or to places where you may be able to collect gemstones.

A list of Selected references on rocks, minerals, and gemstones is compiled and updated every two years by the USGS Geologic Inquiries Group, 907 National Center, Reston, VA 22092; (703) 648-4383. The list has three sections: selected guides for rockhounds and hobbyists, general references for all ages, elementary school to adult, and periodicals.

The guides in Section I tell about equipment needed for collecting, etiquette of collecting, map reading, organizing a collection, collecting localities by States, mineral societies, mineral show dates and locations, and rock, mineral, and fossil dealers.

The references below focus mainly on natural gemstones and the gems made from them rather than on synthetic gemstones, rocks, or other nongem minerals.

Minerals Yearbook

The relatively few pages on gemstones in the multivolume Minerals Yearbook provide data on sources, kinds, and volume of domestic production, domestic consumption, prices, and foreign trade. This U.S. Bureau of Mines yearbook is in the reference sections of many major libraries. It can be purchased from the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402.

Books

Gemology, Cornelius S. Hurlbut Jr. and Robert C. Kammerling: John Wiley & Sons, New York, 1991, 2nd ed.

Gemstones and Their Origins, Peter C. Keller: Van Nostrand Reinhold, 1990.

Color Encyclopedia of Gemstones, Joel Arem: Van Nostrand Reinhold, New York, 1987, 2nd ed., 68 p.

Gemstones for Everyman, B.W. Anderson: Van Nostrand Reinhold, 1976, 268 p.

Gems and Precious Stones, Curzio Cipriani and Alessandro Boreli; Valerie Palmer, translator: Kennie Lyman, U.S. editor: Simon and Schuster, New York, 1986, 384 p.

Gem and Crystal Treasures, Peter Bancroft: Mineralogical Record, Carson City, NV, 1984, 488 p.

Planet Earth—Gemstones, Paul O’Neil and the editors of Time-Life Books: Time-Life Books, Arlington, VA, 1983, 176 p.

Gemstones of the World, Walter Schumann (translated by Evelyne Stern): Sterling, New York, 1984, 256 p.

Gems & Crystals from the American Museum of Natural History: An illustrated guide to the history, lore, and properties of the gems and minerals of one of the world’s greatest collections, Anna S. Sofiandes and George E. Harlow: Simon & Schuster, New York, 1990, 208 p.

The Gem Collection (Treasures in the Smithsonian Series No. 1), P.E. Desautels: Smithsonian Institution, Washington, 1983, 77 p.

Gemstones of North America, John Sinkankas: D. Van Nostrand Company, Inc., Princeton, 1959, 675 p.

Gems and Precious Stones of North America—A popular description of their occurrence, value, history, archeology, and of collections in which they exist, G.F. Kunz: Dover Publishing, New York, 1968 (reprint of a classic work dated 1892), 367 p.

Emerald and Other Beryls, John Sinkankas: Chilton Way, Radnor, PA, 1981, 665 p.

Handbook of Gem Identification, R.T. Liddicoat Jr.: Gemological Institute of America, Santa Monica, CA, 1981 (11th ed.), 450 p.

Field Collecting Gemstones and Minerals, John Sinkankas: Geoscience Press, Prescott, AZ, 1988, 2nd ed., 397 p.

Prospecting for Gemstones and Minerals [Formerly Gemstones and Minerals: How and Where to Find Them], John Sinkankas: Van Nostrand Reinhold, New York, 1970, 2nd ed., 397 p.

Mineral & Gem Trails of Delaware, Virginia, Maryland, North Carolina, Ed and Bert Sloan: EDSCO, Box 79, Oneonta, NY 13820, 1978, 52 p.

Gem Testing, B.W. Anderson: Butterworth, Woburn, MA, 1980, 9th ed., 384 p.

Gemology, C.S. Hurlbut Jr. and G.S. Switzer: Wiley, New York, 1979, 596 p.

Gems and Jewelry, Joel Arem: Bantam Books, New York, 1975, 159 p.

Gem Cutting: A Lapidary’s Manual, John Sinkankas: Van Nostrand Reinhold, New York, 1962, 2nd ed., 297 p.

Lavender-hued rose quartz, Brazil.

Journals

Gems and Gemology (quarterly). Articles on gemstone localities, identification, and history. Includes annual index, lab notes, book reviews, and gemological abstracts. Published by the Gemological Institute of America, 1660 Stewart Street, Santa Monica, CA 90404.

Lapidary Journal (monthly). Articles on gemstones, locality information, expeditions to find sources of gemstones, gemcraft, club news, show news, product news, and book reviews. Published by the Lapidary Journal, Devon Office Center, Suite 201, 60 Chestnut Avenue, Devon, PA 19333-1312.

Rocks & Minerals (bimonthly). Features articles of interest to students of mineralogy, geology, and paleontology. Includes articles about gemstone localities. Regularly lists announcements of hundreds of mineral, rock, and gem shows (local, State, national, Canadian, and European). Includes media reviews, museum notes and announcements, and classified ads. Published by Heldref Publications, 4000 Albermarle Street, NW., Washington, DC 20016.

Jewelers’ Book Club—Catalog (annual). Catalog of more than 550 jewelry-related publications from more than 250 publishers. Includes video- and audio-cassettes and book reviews. Jewelers’ Book Club—News (quarterly) informs members of new titles and provides book reviews. Published by the Jewelers Book Club, Chilton Way, Radnor, PA 19089.

Videocassettes

Gemstones of America (60 minutes), Smithsonian Institution, 1991, can be ordered for $29.95 from the Museum Shop, Attention: Mail Order Clerk, National Museum of Natural History, 10th Street and Constitution Avenue, NW., Washington, DC 20560; (202) 357-1535.

Splendid Stones. This National Geographic Society special details the evolution from raw material to cut and polished gem, outlines many of the steps involved in marketing gemstones, and examines some of the world’s most famous jewelry collections. It can be ordered for $95 from the National Geographic Society, 17th and M Streets NW., Washington, DC 20036.

Acknowledgments

The U.S. Geological Survey is grateful to the following individuals for their assistance:

Harvey E. Belkin, Geologist, Geological Survey, U.S. Department of the Interior, Reston, VA.

Gordon T. Austin, “Gem Stones,” Mineral Commodity Summaries 1991, Bureau of Mines, U.S. Department of the Interior, Washington, DC.

Robert E. Thaden, “Gem Stones,” in United States Mineral Resources, Geological Survey Professional Paper 820, U.S. Government Printing Office, Washington, 1973, p. 247-250.

Jane Jenness, Minerals Information Office, U.S. Geological Survey, Washington, DC.

Photographs

All photographs are courtesy of The Smithsonian Institution.

Transcriber’s Notes

- Retained publication information from the printed edition: this eBook is public-domain in the country of publication.

- In the text versions only, text in italics is delimited by _underscores_.

- In the ASCII version only, subscripted numbers are preceded by underscore and delimited by brackets.

*** END OF THE PROJECT GUTENBERG EBOOK NATURAL GEMSTONES ***

Updated editions will replace the previous one—the old editions will be renamed.

Creating the works from print editions not protected by U.S. copyright law means that no one owns a United States copyright in these works, so the Foundation (and you!) can copy and distribute it in the United States without permission and without paying copyright royalties. Special rules, set forth in the General Terms of Use part of this license, apply to copying and distributing Project Gutenberg™ electronic works to protect the PROJECT GUTENBERG™ concept and trademark. Project Gutenberg is a registered trademark, and may not be used if you charge for an eBook, except by following the terms of the trademark license, including paying royalties for use of the Project Gutenberg trademark. If you do not charge anything for copies of this eBook, complying with the trademark license is very easy. You may use this eBook for nearly any purpose such as creation of derivative works, reports, performances and research. Project Gutenberg eBooks may be modified and printed and given away—you may do practically ANYTHING in the United States with eBooks not protected by U.S. copyright law. Redistribution is subject to the trademark license, especially commercial redistribution.

START: FULL LICENSE

THE FULL PROJECT GUTENBERG LICENSE

PLEASE READ THIS BEFORE YOU DISTRIBUTE OR USE THIS WORK

To protect the Project Gutenberg™ mission of promoting the free distribution of electronic works, by using or distributing this work (or any other work associated in any way with the phrase “Project Gutenberg”), you agree to comply with all the terms of the Full Project Gutenberg™ License available with this file or online at www.gutenberg.org/license.

Section 1. General Terms of Use and Redistributing Project Gutenberg™ electronic works

1.A. By reading or using any part of this Project Gutenberg™ electronic work, you indicate that you have read, understand, agree to and accept all the terms of this license and intellectual property (trademark/copyright) agreement. If you do not agree to abide by all the terms of this agreement, you must cease using and return or destroy all copies of Project Gutenberg™ electronic works in your possession. If you paid a fee for obtaining a copy of or access to a Project Gutenberg™ electronic work and you do not agree to be bound by the terms of this agreement, you may obtain a refund from the person or entity to whom you paid the fee as set forth in paragraph 1.E.8.

1.B. “Project Gutenberg” is a registered trademark. It may only be used on or associated in any way with an electronic work by people who agree to be bound by the terms of this agreement. There are a few things that you can do with most Project Gutenberg™ electronic works even without complying with the full terms of this agreement. See paragraph 1.C below. There are a lot of things you can do with Project Gutenberg™ electronic works if you follow the terms of this agreement and help preserve free future access to Project Gutenberg™ electronic works. See paragraph 1.E below.

1.C. The Project Gutenberg Literary Archive Foundation (“the Foundation” or PGLAF), owns a compilation copyright in the collection of Project Gutenberg™ electronic works. Nearly all the individual works in the collection are in the public domain in the United States. If an individual work is unprotected by copyright law in the United States and you are located in the United States, we do not claim a right to prevent you from copying, distributing, performing, displaying or creating derivative works based on the work as long as all references to Project Gutenberg are removed. Of course, we hope that you will support the Project Gutenberg™ mission of promoting free access to electronic works by freely sharing Project Gutenberg™ works in compliance with the terms of this agreement for keeping the Project Gutenberg™ name associated with the work. You can easily comply with the terms of this agreement by keeping this work in the same format with its attached full Project Gutenberg™ License when you share it without charge with others.

1.D. The copyright laws of the place where you are located also govern what you can do with this work. Copyright laws in most countries are in a constant state of change. If you are outside the United States, check the laws of your country in addition to the terms of this agreement before downloading, copying, displaying, performing, distributing or creating derivative works based on this work or any other Project Gutenberg™ work. The Foundation makes no representations concerning the copyright status of any work in any country other than the United States.

1.E. Unless you have removed all references to Project Gutenberg:

1.E.1. The following sentence, with active links to, or other immediate access to, the full Project Gutenberg™ License must appear prominently whenever any copy of a Project Gutenberg™ work (any work on which the phrase “Project Gutenberg” appears, or with which the phrase “Project Gutenberg” is associated) is accessed, displayed, performed, viewed, copied or distributed:

This eBook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.org. If you are not located in the United States, you will have to check the laws of the country where you are located before using this eBook.

1.E.2. If an individual Project Gutenberg™ electronic work is derived from texts not protected by U.S. copyright law (does not contain a notice indicating that it is posted with permission of the copyright holder), the work can be copied and distributed to anyone in the United States without paying any fees or charges. If you are redistributing or providing access to a work with the phrase “Project Gutenberg” associated with or appearing on the work, you must comply either with the requirements of paragraphs 1.E.1 through 1.E.7 or obtain permission for the use of the work and the Project Gutenberg™ trademark as set forth in paragraphs 1.E.8 or 1.E.9.

1.E.3. If an individual Project Gutenberg™ electronic work is posted with the permission of the copyright holder, your use and distribution must comply with both paragraphs 1.E.1 through 1.E.7 and any additional terms imposed by the copyright holder. Additional terms will be linked to the Project Gutenberg™ License for all works posted with the permission of the copyright holder found at the beginning of this work.

1.E.4. Do not unlink or detach or remove the full Project Gutenberg™ License terms from this work, or any files containing a part of this work or any other work associated with Project Gutenberg™.

1.E.5. Do not copy, display, perform, distribute or redistribute this electronic work, or any part of this electronic work, without prominently displaying the sentence set forth in paragraph 1.E.1 with active links or immediate access to the full terms of the Project Gutenberg™ License.

1.E.6. You may convert to and distribute this work in any binary, compressed, marked up, nonproprietary or proprietary form, including any word processing or hypertext form. However, if you provide access to or distribute copies of a Project Gutenberg™ work in a format other than “Plain Vanilla ASCII” or other format used in the official version posted on the official Project Gutenberg™ website (www.gutenberg.org), you must, at no additional cost, fee or expense to the user, provide a copy, a means of exporting a copy, or a means of obtaining a copy upon request, of the work in its original “Plain Vanilla ASCII” or other form. Any alternate format must include the full Project Gutenberg™ License as specified in paragraph 1.E.1.

1.E.7. Do not charge a fee for access to, viewing, displaying, performing, copying or distributing any Project Gutenberg™ works unless you comply with paragraph 1.E.8 or 1.E.9.

1.E.8. You may charge a reasonable fee for copies of or providing access to or distributing Project Gutenberg™ electronic works provided that:

- • You pay a royalty fee of 20% of the gross profits you derive from the use of Project Gutenberg™ works calculated using the method you already use to calculate your applicable taxes. The fee is owed to the owner of the Project Gutenberg™ trademark, but he has agreed to donate royalties under this paragraph to the Project Gutenberg Literary Archive Foundation. Royalty payments must be paid within 60 days following each date on which you prepare (or are legally required to prepare) your periodic tax returns. Royalty payments should be clearly marked as such and sent to the Project Gutenberg Literary Archive Foundation at the address specified in Section 4, “Information about donations to the Project Gutenberg Literary Archive Foundation.”

- • You provide a full refund of any money paid by a user who notifies you in writing (or by e-mail) within 30 days of receipt that s/he does not agree to the terms of the full Project Gutenberg™ License. You must require such a user to return or destroy all copies of the works possessed in a physical medium and discontinue all use of and all access to other copies of Project Gutenberg™ works.

- • You provide, in accordance with paragraph 1.F.3, a full refund of any money paid for a work or a replacement copy, if a defect in the electronic work is discovered and reported to you within 90 days of receipt of the work.

- • You comply with all other terms of this agreement for free distribution of Project Gutenberg™ works.

1.E.9. If you wish to charge a fee or distribute a Project Gutenberg™ electronic work or group of works on different terms than are set forth in this agreement, you must obtain permission in writing from the Project Gutenberg Literary Archive Foundation, the manager of the Project Gutenberg™ trademark. Contact the Foundation as set forth in Section 3 below.

1.F.

1.F.1. Project Gutenberg volunteers and employees expend considerable effort to identify, do copyright research on, transcribe and proofread works not protected by U.S. copyright law in creating the Project Gutenberg™ collection. Despite these efforts, Project Gutenberg™ electronic works, and the medium on which they may be stored, may contain “Defects,” such as, but not limited to, incomplete, inaccurate or corrupt data, transcription errors, a copyright or other intellectual property infringement, a defective or damaged disk or other medium, a computer virus, or computer codes that damage or cannot be read by your equipment.

1.F.2. LIMITED WARRANTY, DISCLAIMER OF DAMAGES - Except for the “Right of Replacement or Refund” described in paragraph 1.F.3, the Project Gutenberg Literary Archive Foundation, the owner of the Project Gutenberg™ trademark, and any other party distributing a Project Gutenberg™ electronic work under this agreement, disclaim all liability to you for damages, costs and expenses, including legal fees. YOU AGREE THAT YOU HAVE NO REMEDIES FOR NEGLIGENCE, STRICT LIABILITY, BREACH OF WARRANTY OR BREACH OF CONTRACT EXCEPT THOSE PROVIDED IN PARAGRAPH 1.F.3. YOU AGREE THAT THE FOUNDATION, THE TRADEMARK OWNER, AND ANY DISTRIBUTOR UNDER THIS AGREEMENT WILL NOT BE LIABLE TO YOU FOR ACTUAL, DIRECT, INDIRECT, CONSEQUENTIAL, PUNITIVE OR INCIDENTAL DAMAGES EVEN IF YOU GIVE NOTICE OF THE POSSIBILITY OF SUCH DAMAGE.

1.F.3. LIMITED RIGHT OF REPLACEMENT OR REFUND - If you discover a defect in this electronic work within 90 days of receiving it, you can receive a refund of the money (if any) you paid for it by sending a written explanation to the person you received the work from. If you received the work on a physical medium, you must return the medium with your written explanation. The person or entity that provided you with the defective work may elect to provide a replacement copy in lieu of a refund. If you received the work electronically, the person or entity providing it to you may choose to give you a second opportunity to receive the work electronically in lieu of a refund. If the second copy is also defective, you may demand a refund in writing without further opportunities to fix the problem.

1.F.4. Except for the limited right of replacement or refund set forth in paragraph 1.F.3, this work is provided to you ‘AS-IS’, WITH NO OTHER WARRANTIES OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY PURPOSE.

1.F.5. Some states do not allow disclaimers of certain implied warranties or the exclusion or limitation of certain types of damages. If any disclaimer or limitation set forth in this agreement violates the law of the state applicable to this agreement, the agreement shall be interpreted to make the maximum disclaimer or limitation permitted by the applicable state law. The invalidity or unenforceability of any provision of this agreement shall not void the remaining provisions.

1.F.6. INDEMNITY - You agree to indemnify and hold the Foundation, the trademark owner, any agent or employee of the Foundation, anyone providing copies of Project Gutenberg™ electronic works in accordance with this agreement, and any volunteers associated with the production, promotion and distribution of Project Gutenberg™ electronic works, harmless from all liability, costs and expenses, including legal fees, that arise directly or indirectly from any of the following which you do or cause to occur: (a) distribution of this or any Project Gutenberg™ work, (b) alteration, modification, or additions or deletions to any Project Gutenberg™ work, and (c) any Defect you cause.

Section 2. Information about the Mission of Project Gutenberg™

Project Gutenberg™ is synonymous with the free distribution of electronic works in formats readable by the widest variety of computers including obsolete, old, middle-aged and new computers. It exists because of the efforts of hundreds of volunteers and donations from people in all walks of life.

Volunteers and financial support to provide volunteers with the assistance they need are critical to reaching Project Gutenberg™’s goals and ensuring that the Project Gutenberg™ collection will remain freely available for generations to come. In 2001, the Project Gutenberg Literary Archive Foundation was created to provide a secure and permanent future for Project Gutenberg™ and future generations. To learn more about the Project Gutenberg Literary Archive Foundation and how your efforts and donations can help, see Sections 3 and 4 and the Foundation information page at www.gutenberg.org.

Section 3. Information about the Project Gutenberg Literary Archive Foundation

The Project Gutenberg Literary Archive Foundation is a non-profit 501(c)(3) educational corporation organized under the laws of the state of Mississippi and granted tax exempt status by the Internal Revenue Service. The Foundation’s EIN or federal tax identification number is 64-6221541. Contributions to the Project Gutenberg Literary Archive Foundation are tax deductible to the full extent permitted by U.S. federal laws and your state’s laws.

The Foundation’s business office is located at 809 North 1500 West, Salt Lake City, UT 84116, (801) 596-1887. Email contact links and up to date contact information can be found at the Foundation’s website and official page at www.gutenberg.org/contact

Section 4. Information about Donations to the Project Gutenberg Literary Archive Foundation

Project Gutenberg™ depends upon and cannot survive without widespread public support and donations to carry out its mission of increasing the number of public domain and licensed works that can be freely distributed in machine-readable form accessible by the widest array of equipment including outdated equipment. Many small donations ($1 to $5,000) are particularly important to maintaining tax exempt status with the IRS.

The Foundation is committed to complying with the laws regulating charities and charitable donations in all 50 states of the United States. Compliance requirements are not uniform and it takes a considerable effort, much paperwork and many fees to meet and keep up with these requirements. We do not solicit donations in locations where we have not received written confirmation of compliance. To SEND DONATIONS or determine the status of compliance for any particular state visit www.gutenberg.org/donate.

While we cannot and do not solicit contributions from states where we have not met the solicitation requirements, we know of no prohibition against accepting unsolicited donations from donors in such states who approach us with offers to donate.

International donations are gratefully accepted, but we cannot make any statements concerning tax treatment of donations received from outside the United States. U.S. laws alone swamp our small staff.

Please check the Project Gutenberg web pages for current donation methods and addresses. Donations are accepted in a number of other ways including checks, online payments and credit card donations. To donate, please visit: www.gutenberg.org/donate.

Section 5. General Information About Project Gutenberg™ electronic works

Professor Michael S. Hart was the originator of the Project Gutenberg™ concept of a library of electronic works that could be freely shared with anyone. For forty years, he produced and distributed Project Gutenberg™ eBooks with only a loose network of volunteer support.

Project Gutenberg™ eBooks are often created from several printed editions, all of which are confirmed as not protected by copyright in the U.S. unless a copyright notice is included. Thus, we do not necessarily keep eBooks in compliance with any particular paper edition.

Most people start at our website which has the main PG search facility: www.gutenberg.org.

This website includes information about Project Gutenberg™, including how to make donations to the Project Gutenberg Literary Archive Foundation, how to help produce our new eBooks, and how to subscribe to our email newsletter to hear about new eBooks.

Table of Contents

Natural Gemstones

Natural gemstones

Geologic environment

Gemstones occur in most major geologic environments.

Mineral gemstones

Birthstones

Organic gemstones

Buyer beware

Since 1935, the mining of gemstones in the United States has been almost entirely a recreational activity of mineral collectors and hobbyists.

The 1990 U.S. output of natural gemstones was primarily from Tennessee, California, Arizona, Arkansas, Montana, Nevada, and Maine.

Gemstones: Value of U.S. production vs. imports, 1986 and 1989[1]

Except for the few gem diamonds found each year in Arkansas, U.S. diamond production is very low.

World diamond reserves are estimated to be about 300 million carats, including near-gem materials but not diamonds of abrasive quality.

Chemical formulas of gemstones

Some ways to contact a local rock, mineral, or gem club

Role of the U.S. Geological Survey (USGS)

Selected general references

Acknowledgments

Photographs

Transcriber’s Notes

THE FULL PROJECT GUTENBERG LICENSE