Gemstone Basics

How to Select the Perfect Gem

As with diamonds, gemstone value and quality are evaluated according to the Four C's: color, clarity, cut, and carat weight. Obviously, color is the most important factor for gemstones. Clarity refers to how clear the gemstone is and how free of flaws (inclusions) it is. While diamonds are cut to provide the most sparkle, gemstones are cut to display even color and have the least amount of flaws. Because gems have varying weights, stones that are the same size will oftentimes have different weights.

Common gemstones

Certain gemstones have been associated with months of the year. Called birthstones, many people enjoy receiving their particular birthstone jewelry.

Birthstone Chart

    Garnet            Amethyst               Aquamarine               Diamond  

Garnet (January)         Amethyst (February)   Aquamarine (March)   Diamond (April)

 

 

Emerald                  Pearl                Ruby                     Peridot 

Emerald (May)            Pearl (June)                 Ruby (July)                 Peridot (August)

 

 Sapphire                    Opal                      November                     Blue Topaz

Sapphire (September)  Opal (October)            November (Citrine)     Blue Topaz (December)

Determining a Gem's Durability: The Mohs Scale of Hardness

Gems are minerals that have been cut and polished. The Mohs scale of mineral hardness lists the scratch resistance and durability of minerals and gems, which have different levels of relative hardness. The harder a gem, the more durable and scratch resistant it is. According to the Mineralogical Society of America, the direction of the scratch can vary the level of hardness.


This scale is an ordinal scale in that it refers to the order structure. A diamond has a hardness of 10 while topaz is listed at an 8.  Diamond (10) is almost four times as hard as corundum (9), which is twice as hard as topaz (8).


Scale of Hardness

Gem Graph

Hardness

Gemstone

10

Diamond

9

Ruby, sapphire

8

Topaz

7.5

Emerald, Aquamarine

7

Amethyst

6.5

Peridot

5.5 – 6.5

Opal

3

Onyx

 

 

 







There are many factors to consider when purchasing gemstone jewelry. You’ll want to think about the type of stone to buy based on the color, the coinciding birth month, and/or the hardness of the gem.