Hard Facts about Gemstones

In the game of rock, paper, scissors you almost always know where you stand. Paper always smothers rock, scissors always slice paper, and rock always crushes the shears, but what happens when rock meets rock? Well, that depends on the type of mineral your hand represents!
While settling playground disputes was probably not his inspiration, German mineralogist Friedrich Mohs created a scale to gauge the hardness of minerals. The process is simple-- if one mineral can scratch another, it is harder. Although the Mohs scale is very useful, it is not linear. The minerals chosen were only selected because of their popularity at the time. For example, number ten on the scale, diamond,  is 140 times harder than number nine, corundum, whereas number four, fluorite, is only 1.11 times harder than number three, calcite. A proportional measurement, called absolute hardness, was more recently devised, but is only used by scientists who need extremely accurate results. The Mohs scale satisfies the needs of almost all mineral enthusiasts.
Since most of us don't carry samples of each mineral on the scale, there is a simple test you can perform in your workspace, or deep within your backyard gypsum quarry if you don't have a material. It involves these convenient standards of hardness: soft (can be scratched with a fingernail), medium (can be scratched with a knife or glass but not by a fingernail) or hard (cannot be scratched by a knife).
Sure, you might have to wrestle your best friend if they don't accept that your hand is made of diamond and theirs is talc in a game of rock, paper, scissors, but you'll never have to grapple with worries that a gemstone in your collection is anything but the genuine article.
Here is a reference for the Mohs Hardness Scale:
↓ Mohs hardness               Absolute Hardness  ↓
1         Talc                             1
2         Gypsum                       3
3         Calcite                         9
4         Fluorite                        21
5         Apatite                        48
6         Feldspar                      72
7         Quartz                        100
8         Topaz                         200
9         Corundum                  400
10       Diamond                    1600
by Zachary Frazee