What is Specific Gravity? Specific gravity is the ratio of a mineral’s density compared to water (relative density). In the field it’s often estimated by “heft,” and at home it can be measured with a small scale and water displacement. Specific gravity helps confirm minerals that look similar but feel noticeably heavier or lighter. Because pores, vugs, and coatings can change the feel, test a solid piece when you can.
For Specific Gravity, make your field notes comparative (“heavier than quartz,” “much heavier than expected”) because that stays useful even without a number. If you measure at home, avoid trapped bubbles and fully dry the specimen afterward so you don’t store moisture in cracks. Use a dense fragment when possible; porous material can read artificially low. Specific gravity is especially valuable when two candidates share color and luster but differ strongly in density.
Specific Gravity vs. size Bigger pieces feel heavier even when the material is light. Compare equal-sized fragments when using heft.
Specific Gravity vs. porosity Vugs and pores reduce apparent density. Use a solid fragment for a more reliable result.
Specific Gravity vs. metallic look Metallic luster does not guarantee high density. Record heft directly instead of assuming.
Specific Gravity vs. a wet specimen Water in pores can change feel and measurements. Dry the specimen before relying on the result.