Category Gemstones

Idaho Gemstone Mining
Gemstones

Idaho Gemstone Mining

Garnet and opal are Idaho's most important gems, but many others have been produced in the state. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Idaho Harlequin Opal: Photo of a harlequin opal triplet from the Constellation Mine near Spencer, Idaho. It is 6 millimeters by 4 millimeters in size.

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Gemstones

Carnelian Gemstones

Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Carnelian gemstone: A tumble-polished carnelian with typical translucent diaphaneity. Image copyright iStockphoto / Arpad Benedek. What is Carnelian? Carnelian agate is a name given to a translucent orange to red to brown chalcedony. It is frequently a banded material with bands of red to orange chalcedony alternating with bands of white agate.
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Gemstones

Ruby and Sapphire

Red corundums are rubies. Blue corundums are sapphires. Trace elements produce their colors. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Rubies: The most desired variety of corundum is the ruby. The red color is produced by trace amounts of chromium in the mineral. These two beautiful rubies were mined in Madagascar.
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Gemstones

Moldavite

A green gem formed by an ancient asteroid impact Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Moldavite: Two faceted specimens of moldavite. They both exhibit the bubbles and flow lines expected in a glass formed by a violent impact. Both of these gems measure 10 x 8 millimeters. The gem on the left weighs 2.
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Gemstones

Ammolite

An organic gemstone with a spectacular flash of iridescent colors! Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Ammolite cabochons: Three Ammolite cabochons made from material mined from the Bearpaw Formation at the Aurora Ammolite Mine in Alberta, Canada. All of these cabochons are assembled triplet stones with a transparent quartz cap.
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Gemstones

Idaho Gemstone Mining

Garnet and opal are Idaho's most important gems, but many others have been produced in the state. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Idaho Harlequin Opal: Photo of a harlequin opal triplet from the Constellation Mine near Spencer, Idaho. It is 6 millimeters by 4 millimeters in size.
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Gemstones

Oregon Gemstone Mining

Oregon is a leading state for gemstone production with sunstone, thundereggs, opal and more. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Two specimens of Oregon Sunstone: The specimen on the left is a round cabochon weighing 2.29 carats and about 7mm in diameter. It is a stone that is heavily included with visible platelets of copper.
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Gemstones

Harlequin Opal

Pictures of beautiful harlequin opals Harlequin opal: Photo of a harlequin opal from the Constellation Mine in Spencer, Idaho. It is 6 millimeters by 4 millimeters in size. What is a Harlequin Opal? "Harlequin opal" is a name given to an opal with patches of fire in the shape of rectangles or diamonds.
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Gemstones

Amethyst

The world's most popular purple gemstone Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Faceted amethyst: Four faceted amethysts in trillion, pear, round and oval shapes. Table of Contents What is Amethyst? Color in Amethyst Amethyst Crystals Physical Properties of Amethyst Geologic Occurrence of Amethyst Amethyst by the Ton Ametrine Amethyst Treatment to Citrine and Prasiolite Care of Amethyst Gems and Jewelry Synthetic Amethyst Amethyst Simulants Amethyst as a Healing Stone?
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Gemstones

Heliodor

Also known as golden beryl or yellow beryl. Inappropriately as yellow emerald. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Heliodor: A round faceted heliodor with a golden-yellow color from Madagascar, measuring 5.97 millimeters in diameter and weighing 0.72 carats. What is Heliodor? Heliodor is a name used by mineralogists and gemologists for specimens of the mineral beryl with a yellow, greenish yellow, or golden-yellow color.
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Gemstones

Cat's-Eye Opal

Pictures of Cat's-Eye Opal Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Cat's-Eye Opal: This yellow-orange cat's-eye opal was cut from rough mined in Madagascar. It measures 13.6 x 11.3 x 6.9 millimeters in size and weighs 5.98 carats. If you look closely you might be able to perceive that the parallel mineral fibers cross the line of the eye at a right angle.
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Gemstones

Organic Gemstones

Some are composed of organic materials, some are fossilized organic structures. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Organic Gemstones: This colorful collage features some of the organic gems of this article. Starting at the top and moving to the left are: amber, ammolite, fossil coral, petrified wood, fossil stromatolite, mother of pearl, fossil sand dollar, turritella agate, freshwater cultured pearls, fossil dinosaur bone, fossil crinoidal limestone, red coral, fossil ammonite, peanut wood, jet, and opalized wood.
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Gemstones

Tiger's-Eye Gemstones

Also known as "Tiger Eye" and "Tigers Eye" Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Brown tiger's-eye cabochon: Brown banded tiger's-eye cut into an oval cabochon. Image copyright . What is Tiger's-Eye? Tiger's-eye, also called "tiger eye" and "tigers eye," is a very popular gemstone that displays a chatoyancy (cat's-eye) when a polished stone is moved back and forth in incident light.
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Gemstones

Turritella Agate

Named "Turritella" in error decades ago. The correct name would be "Elimia Agate." Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Turritella Agate / Elimia Agate: A close-up photo of a sawn surface of Turritella Agate showing numerous spiral-shaped snail shells. This type of view shows how the internal cavities of the shells and the voids between the shells have all been infilled with the translucent-to-transparent agate.
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Gemstones

White Opal: Also Known as Light Opal

Pictures and video of white opals White Opal: Two white opals cut from material mined in Coober Pedy, South Australia. They are calibrated cabochons measuring 8 x 6 millimeters. What is White Opal? "Light opal" and "white opal" are terms used for opal material that has a white, yellow or cream body color.
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Gemstones

California Gemstone Mining

California produces a variety of gemstones but is especially known for its tourmaline. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist California Tourmalines: Three beautiful tourmaline crystals from pegmatites in southern California. The green elbaite is from the Little Three Mine near Ramona in San Diego County.
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Gemstones

Gemstone Mining in the United States

A wide variety of gemstones are found throughout the United States Author: Hobart M. King, Ph.D., GIA Graduate Gemologist U.S. Gemstones: A diversity of gemstones are produced from mines throughout the United States. Top row: malachite and azurite cabochon (Arizona), a rough ruby (North Carolina), a faceted orange sunstone (Oregon), a teardrop variscite cabochon (Utah).
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Gemstones

Louisiana Gemstone Mining

Petrified palm wood is found in Louisiana, along with a unique variety of precious opal. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Louisiana palm: An oval cabochon cut from Louisiana palm. The face of the cabochon was cut parallel to the trunk of the palm. The lines represent the vascular structure of the plant.
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Gemstones

"Whitby" Jet

A black organic gem material that is also a rock very similar to coal. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Faceted jet: Four stones of faceted jet from the Whitby area of England. These stones clearly show how jet can accept a highly reflective polish. The round stone at the bottom of this photo is about 12 millimeters in diameter.
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Gemstones

Colorado Gemstone Mining

Most people are surprised to learn that diamonds and many other gems have been mined in Colorado! Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Colorado Rhodochrosite: Rhodochrosite is the official state mineral of Colorado. Sometimes, nice transparent specimens can be found that are suitable for cutting faceted stones.
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