Ice counts as a mineral, liquid water does not, and mercury gets a pass
Mineralogists keep a strict rulebook. A mineral must form naturally, be solid, have ordered atoms and a fairly fixed recipe. So ice qualifies but water does not, seashells are excluded, and a crystal born from bat guano can make the list. Liquid mercury stays in only because it was grandfathered in.
Broadly, a mineral is a naturally occurring solid with a reasonably well-defined chemical composition and a specific crystal structure. A rock is something else: a bulk material made of one or several minerals, or sometimes of non-mineral matter, as coal is. Substances without a crystal lattice, such as opal and obsidian, are called mineraloids. The same compound can yield several minerals if its atoms pack differently; quartz and stishovite are both silicon dioxide.
The International Mineralogical Association sets the rules and, as of August 2026, recognises roughly 6,200 species. Things made purely by people or living bodies, such as tungsten carbide, kidney stones or seashells, are ruled out, but substances whose formation involved geological processes can qualify, like taranakite, which derives from bat guano, or alpersite from mine tailings. Stability at room temperature is not required: meridianiite counts even though it exists only below 2 degrees Celsius. Native mercury, which solidifies only below minus 39 degrees, keeps its status because it was listed before the current rules. The exclusion of biominerals is contested; scientists such as Lowenstam and Skinner argue organisms make genuine minerals, over 60 of which had been named before the official list.
Most species are named after people, followed by places, and most names end in -ite, except old names such as galena and diamond. Varieties can carry their own names too: amethyst is simply purple quartz. The olivine series is split arbitrarily into separate magnesium-rich and iron-rich minerals, forsterite and fayalite. One oddity, icosahedrite, is a natural quasicrystal whose atoms are ordered but never repeat.
Silicates make up about 90 percent of Earth's crust, and the main rock-forming minerals, quartz, feldspars, micas, amphiboles, pyroxenes and olivines, are all silicates, with calcite the exception. Ores such as cinnabar for mercury and cassiterite for tin concentrate the metals that industry needs.
Source: Mineral
