Specific Gravity Testing Part 4: Refining Your Specific Gravity Testing Techniques


Step 3: Practical Gemology

Lesson 10

calcite with hematite inclusions - specific gravity testing techniques
Hematite inclusions in a gem, like this calcite, can add color and interest. However, if present in significant quantities, they can also complicate the measurement of its specific gravity. “Calcite (Fluorescent) with Hematite,” Beckermet Mine, Egremont, West Cumberland Iron Field, Cumbria, England, UK. © Rob Lavinsky, www.iRocks.com. Used with permission.

Getting accurate readings when testing gemstone specific gravity is critical. If you make an error of 0.01 carats weighing a 10-carat gem, it will only affect the results by 0.03. That’s not significant. However, on a 1-carat stone, a 0.01 weight error will make a 0.08 difference in your specific gravity calculations. That’s enough to misidentify some stones. On a half-carat stone, the same error changes the specific gravity reading by 0.13. With smaller gems, errors lead to …

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