Specific Gravity Ranges for Minerals

Specific gravity expresses the relative density of a material relative to the density of water. Water is defined to have a specific gravity of 1.00. If a material has a specific gravity greater than 1 then it is heavier than water (would sink if placed in water). If the value for specific gravity is less than 1, then the material is less dense than water (would float). Metallic gems and minerals tend to be about twice as heavy as their non-metallic counterparts. Specific gravity is often cited as a range of values because the density of a mineral can vary, even within a single crystal, due to factors such as impurities and inclusions. Specific gravity ranges may be used to categorize minerals according to their weight. In many cases, you can feel the weight difference yourself. For example, a piece of gold may feel noticeably heavier than a similarly-sized piece of pyrite (fool's gold). Another way to look at it is that you get a bigger gemstone per carat of quartz than you do per carat of zircon.

Specific Gravity	Weight Category	Example Minerals
1-2	Lightweight	Borax (1.7) Ulexite (1.9) Kernite (1.95)
2-4	Average Weight or Medium Weight	Sulfur (2.0-2.1) Halite [salt] (2.16) Gypsum (2.3-2.4) Bauxite (2.4-2.6) Orthoclase (2.5-2.6) Quartz [rock crystal] (2.65) Calcite (2.7) Fluorite (3.0-3.2) Realgar (3.5-3.6)
4-6	Heavyweight	Chalcopyrite (4.1-4.3) Barite (4.3-4.6) Stibnite (4.6) Zircon (4.6-4.7) Marcasite (4.8-4.9) Bornite (4.9-5.1) Pyrite (4.9-5.2) Hematite (4.9-5.3)
Over 6	Very Heavy	Colbaltite (6.3) Wulfenite (6.5-7.0) Vanadinite (6.7-7.2) Cassiterite (6.8-7.1) Galena (7.4-7.6) Cinnabar (8.0-8.2) Native Copper (8.9) Native Gold (19.3)

Reference: Mineral Collector's Handbook. Barry Krause. Sterling Publishing Co, Inc. (New York) 1996.

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