These break in an uneven and irregular manner. Hold the specimen in one hand and a sample of quartz of approximately equal size in the other hand. When a laboratory is available you may want a more precise measure of the quantity of matter in the specimen. Specific gravity is the weight of the specimen compared to the weight of an equal volume of water. Density and specific gravity have the same numerical value, differing in unit dimensions.
Some minerals occur in varieties with density ranges rather than a precise value.
The specific gravity of quartz is 2.6, meaning that a chunk of quartz is 2.6 times heavier than an equal volume of water. You do not need to determine the density or specific gravity of specimens in your mineral collection unless it is necessary to distinguish them from some other similar minerals with the same heft. See the double refraction display in the hallway exhibit. For classification and help with identification of specimens, see hallway exhibit. Concentrated HCl is a powerful and dangerous acid.