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Gemstone Information

Read Gemstone Articles at GemSelectIf you're looking for accurate and useful gemstone information, we can help you! Over the years we've put together the most comprehensive library of gemstone information you'll find on the Internet.

As one of the largest online dealers in fine gemstones, we've learned a lot about gems and the gem market. We're still learning every day and we are glad to share our knowledge with everyone who shares our interest in gemstones.

We're located in Chanthaburi, Thailand, an international center for processing and trading colored gemstones. Traders from around the world bring rough stone from the mines to Chanthaburi to be cut and polished. Hundreds of small factories here process the material and we have a chance to buy virtually every type of colored gemstone on the market.

Being an educated buyer is key to finding the gems you want at the best price. To that end, we have created our library of gem information.

If you'd like an overview of all the different gemstone types (with photos), a good place to start is with our gemstone type list. Another good way to view all the gemstones is by color. We have an illustrated chart that will show you all the different gems grouped by color (red, pink, blue, green, yellow, violet, orange, white, brown, gray, black and multicolor).

Once you find the gems that interest you, go to our gem info pages and find the information page for that gemstone. Each information page will tell you the color range in that particular gem, where deposits are found, and whether the gem is routinely treated. You also find useful gemological data about each gem and the legends and lore associated with it throughout history.

If you're interested in gemological reference information, we've put together some useful charts and lists to compare different gem varieties. You'll find a refractive index chart for about 60 gemstone varieties and a similar chart for gem hardness. You even find a chart that will show you the dispersion (or 'fire') ratings for all the different gemstones. We've also put together a chart showing the cleavage characteristics of all the different gemstones.

One topic that every buyer should understand is the way that different gemstones vary in density. The technical term for density in gemology is specific gravity and a gemstone with a higher specific gravity will be smaller in the same carat weight than a gem with a lower density. Buyers are sometimes surprised when they buy high density gems like spessartite garnet, zircon and sapphire, all of which have a higher density than diamond.

Information is always useful, but what about useful advice? We are always forthcoming with our opinions about which gems are worth buying and at what price, and what to look for in a fine sapphire, tourmaline or garnet. See our gemstone articles for dozens of pieces written by the GemSelect staff, on topics ranging from best value gemstones to sapphire prices to how to buy gems at wholesale prices.

  • First Published: October-06-2010
  • Last Updated: July-18-2014
  • © 2005-2018 GemSelect.com all rights reserved.
    Reproduction (text or graphics) without the express written consent of GemSelect.com (SETT Company Ltd.) is strictly prohibited.
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Size and Weight

Gems are always measured in Millimeter (mm)

Dimensions are given as;
length x width x depth,
except for round stones which are;
diameter x depth

Select gems by size, not by weight!
Gem varieties vary in density, so carat weight is not a good indication of size

Note: 1ct = 0.2g

Size Comparison Chart