What is the term for the ratio that compares a mineral's weight to the weight of an equal volume of water?

The term that describes the ratio comparing a mineral's weight to the weight of an equal volume of water is specific gravity. Specific gravity is a dimensionless number that tells us how dense a substance is relative to the density of water, which has a specific gravity of 1 at 4 degrees Celsius. This measure is particularly useful in mineralogy and materials science because it allows for easy comparison of mineral densities in a straightforward way, without the need for complex units of mass or weight.

In contrast, density itself is a broader term that refers to mass per unit volume, expressed in units such as grams per cubic centimeter (g/cm³). While density and specific gravity are related, specific gravity specifically utilizes water as a reference point for comparison, making it a more precise term for the context of minerals.

Osmosis, on the other hand, refers to the movement of water across a semipermeable membrane, which is not relevant to the weight comparison of minerals and water. Solubility refers to the ability of a substance to dissolve in a solvent, typically water, and also does not pertain to the weight ratio being discussed.