Category: Gemstones


Montana Gemstone Mining Gemstones

Montana Gemstone Mining

Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Montana sapphires: Beautiful blue sapphires found in Montana. This photo shows nearly 70 carats of natural, untreated sapphire. Each stone is about 0.30 - 0.39 carats. Image used with permission of 46 Degree Resources. Montana: The "Treasure State" One of Montana's popular nicknames is "The Treasure State.

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Strontium Titanate Gemstones

Strontium Titanate

A man-made diamond simulant also known as Fabulite, Diagem, Marvelite, Jewelite, and other trade names. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Strontium Titanate: A faceted strontium titanate showing its very strong "fire" or "dispersion." Light that enters the stone is separated into its component colors, similar to a prism, and exits the stone in a scintillation of color.

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Rose Quartz Gemstones

Rose Quartz

A pink color-variety of the mineral quartz. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Rose Quartz: A rare specimen of rose quartz with a gemmy pink color and recognizable crystals. From the Sapucaia Mine, Minas Gerais, Brazil. The specimen is 11.5 x 7 x 4.5 centimeters in size. Specimen and photo by Arkenstone / www.

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Chatoyant Gems - The Cat's-Eye Phenomenon Gemstones

Chatoyant Gems - The Cat's-Eye Phenomenon

What causes the bright line of reflected light that moves under the surface of a chatoyant gem? Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Cat's-Eye Chrysoberyl: Chrysoberyl is the gem that exhibits the finest "cat's-eye." When the name "cat's-eye" is used alone, it is understood that the speaker is referring to a cat's-eye chrysoberyl.

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Peanut Wood Gemstones

Peanut Wood

An unusual petrified driftwood. A gem material from Australia that has nothing to do with "peanuts." Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Peanut wood slab: A nice slab of peanut wood showing lots of "peanut" markings that were produced by the infilling of boreholes made by clams. This slab is about 12 inches in width and was cut from peanut wood mined in the Kennedy Ranges of Western Australia.

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Tennessee Gemstone Mining Gemstones

Tennessee Gemstone Mining

Cultured freshwater pearls have made Tennessee one of the top ten gemstone-producing states. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Tennessee cultured pearls: Coin-shaped, cultured freshwater pearls in beautiful iridescent shades of gold, pink, and blue. These pearls were produced by the American Pearl Company, the only producer in the United States.

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Maw Sit Sit Gemstones

Maw Sit Sit

The bright green and jet-black gem material often confused with jade Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Maw Sit Sit: A group of maw sit sit cabochons showing the typical bright chrome-green color and interesting black pattern. In cabochons, the black kosmochlor often has a much brighter luster than other parts of the stone.

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Maine Gemstone Mining Gemstones

Maine Gemstone Mining

Maine is one of the world's most famous locations for gem-quality tourmaline, beryl, and quartz. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Maine Tourmaline: Three excellent tourmalines from the Dunton Quarry in Oxford County, Maine. Photo by Thuss Photography, used with permission of the Maine State Museum.

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Opal Doublet or Opal Triplet Gemstones

Opal Doublet or Opal Triplet

Also known as "composite opal" or "assembled opal". "Assembled" or "Composite" Opals: This illustration shows the differences between: (A) solid stones; (B) opal doublets; and (C) opal triplets. "Doublets" are so named because they consist of two parts. "Triplets" are so named because they consists of three parts.

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Helenite Gemstones

Helenite

A novelty colored stone made from the ash of the 1980 Mount St. Helens eruption Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Helenite: Three specimens of faceted helenite in blue, red, and green. These colored stones are faceted ovals about 8 x 6 millimeters in size. They were purchased in 2014 for less than $10 per stone.

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Green Gemstones Gemstones

Green Gemstones

Green is a very popular gemstone color. There are many green gems. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Tsavorite Green garnets? Most people have never heard of tsavorite and would be surprised to learn that it is a green garnet. Tsavorite has a wonderful bright green color, and its clarity is superior to emeralds of much higher price for a similar-size gem.

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Agate Gemstones Gemstones

Agate Gemstones

Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Montana agate: A bright collection of agate cabochons cut from rough found in Montana. They show a diversity of banding patterns and inclusions. What is Agate? Agate is a translucent variety of microcrystalline quartz. It is used as a semiprecious stone when it is of desirable quality and color.

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Unakite Gemstones

Unakite

The pink and pistachio-green granitic gem material. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Unakite Cabochons: Two cabochons cut from unakite. The one on the left consists of approximately equal amounts of green epidote and pink orthoclase feldspar. It measures about 30 x 19 millimeters and is cut from a material with a very coarse grain size.

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Common Opal Occurs in a Spectrum of Colors Gemstones

Common Opal Occurs in a Spectrum of Colors

Don't allow the name “common” to fool you. Common opal is uncommonly colorful. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist A spectrum of common opal colors: Pink opal from Peru; yellow and orangy opal from Australia and Nevada; green opal from Peru and Kenya; Blue opal from Oregon and Peru; purple opal from Mexico.

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Prasiolite and Green Amethyst Gemstones

Prasiolite and Green Amethyst

A leek-green quartz produced by heat-treating amethyst. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Prasiolite and Amethyst: Two faceted stones, prasiolite on the left and amethyst on the right. Prasiolite is a yellowish green to green material that is produced when natural amethyst is heated or irradiated.

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Fancy Sapphire Gemstones

Fancy Sapphire

Sapphires occur in many colors beyond blue. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Fancy Sapphires from Australia: These colorful sapphires were produced at the Capricorn Sapphire Mine in Central Queensland, Australia. The mine produces deep blue sapphires and fancy sapphires in a wide range of yellow, green, and bluish green hues.

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Blue Topaz Gemstones

Blue Topaz

Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Natural Blue Topaz: It is very rare to find topaz with a blue color which was created by nature. This specimen is from Zimbabwe and measures 4.6 x 4.2 x 3.1 centimeters. Specimen and photo by Arkenstone / www.iRocks.com. Table of Contents What Is Blue Topaz?

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Aventurine Gemstones

Aventurine

A translucent quartz or quartzite with sparkling reflections. It occurs in a range of colors. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Translucent Aventurine: A small polished piece of aventurine about three centimeters across that shows the translucence, highly included nature and aventurescence of the material.

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Iris Agate Gemstones

Iris Agate

Iris agate is a finely-banded agate that can produce a rainbow of color from a diffraction grating effect. Figure 1: Two views of a specimen of iris agate. The photo on the left was taken in normal light and displays the color of light reflected from the agate. The photo on the right shows the agate with backlighting.

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What is Jade? Gemstones

What is Jade?

Jadeite and nephrite are materials that have both been called "jade" for thousands of years. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Green Jadeite Buttons: Hand-made, antique Chinese jadeite buttons showing the typical color of quality green jadeite. The jadeite in these buttons was most likely mined in Burma (the Union of Myanmar today).

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