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epidote
Epidote Value, Price, and Jewelry Information
The epidote mineral supergroup contains many related species of interest to collectors. However, epidote itself is the one most likely...
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Faceting Tips for Exotic Gemstones
Some gems are seldom faceted because they're rarely found in nature or rarely used for jewelry. Learn a few tricks...
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Mineralogy of Silicates: Nesosilicates and Sorosilicates
Silicates include well-known minerals such as zircon, topaz, and garnet. Learn how to identify minerals from two silicate sub-groups.
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What is Gemstone Pleochroism?
Some gems show pleochroism, two or three different colors depending on the viewing angle. Learn why this occurs and how...
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Turkish Purple Jade Jewelry
What is Turkish purple jade? Learn about the qualities of this rare, beautiful, and versatile gemstone and see it transformed...
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Table of Gems Ordered by Crystal System
This table contains a selection of minerals gemologists may encounter as jewelry stones or gem specimens. The gems are sorted...
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Destructive Gemstone Tests: Streak Testing
Streak testing is a destructive gemstone test rarely used by gemologists, but it is a standard diagnostic test for mineralogists....
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Table of Refractive Indices and Double Refraction of Selected Gems
Refractive indices and double refraction (birefringence) help gemologists identify gems. The following table lists these values for selected gemstones.
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The Mohs Hardness Scale and Chart for Select Gems
The Mohs hardness scale measures a mineral's resistance to scratching. Find the traditional scale here and a chart of select...
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Gemstone Toxicity Table
Gem faceters and jewelry enthusiasts alike should learn about gemstone toxicity. This table has toxicity ratings for 280+ gems, based...
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What is a Gem?
Even the most general definition of a gem has many exceptions. Learn what qualities have been used to identify gemstones...
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Specific Gravity Values of Selected Gems
Measuring specific gravity helps gemologists identify gemstones. The following table lists the specific gravity values for a variety of gem...
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A Visitor’s Guide to Colorado Gemstones
Colorado has a lot to offer gemologists and rock hunters. Before you visit, learn about Colorado gemstones as well as...
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What is the Usambara Effect In Gemstones?
The Usambara effect is a gemstone color change phenomenon distinct from pleochroism or the alexandrite effect. Tourmaline and other species...
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Gemstone Thermal Properties
Non-destructive tests are critical for gemologists trying to identify gems. Learn how measuring thermal properties, especially thermal inertia, can help....
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Identifying Lab-Made Emeralds
Mined emeralds are expensive, so lab-made emeralds are an attractive option for consumers. Learn how these synthetic gems are made...
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Phenomenal Gems: Cat’s Eyes, Star Stones, and More
Phenomenal gems seem to do magical things with light. Learn the science behind optical effects like cat’s eyes and star...
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Emerald Origins: History and Identification
Emeralds from different sources can vary in quality. Learn how to identify emerald origins by analyzing the optical and physical...
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Gemstone Color Measurements and Specifications
Gemstone color measurements are hard to make with conventional color-order systems. Learn how recent colorimetry tech advances have improved accuracy....
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Gem Price Guide
A guide for the price of various gemstones that is based on various sources for commonly traded goods. However, gems...
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