Built by a geologist
Mineral Crystal Habit Chart
Crystal habit describes the outward shape of an individual mineral crystal or the way many crystals grow together. It is not the same as crystal system, which describes underlying symmetry, and a broken cleavage fragment is not automatically a natural crystal face. Use an intact dry specimen in diffuse light and a hand lens. First decide whether distinct crystals are visible. Equant or blocky crystals have roughly similar dimensions; prismatic or columnar crystals are longer in one direction; tabular and bladed crystals are flattened; acicular crystals are needle-like; fibrous material is made of fibres; botryoidal surfaces resemble rounded clusters; radiating aggregates grow outward from a centre; dendritic growth branches; massive material has no visible outer crystal form; and granular material is an aggregate of grains. Growth space, chemistry, temperature, pressure, impurities, crowding, breakage, and alteration can give one mineral several habits. Fibrous-looking does not prove asbestos, but some natural mineral fibres can be hazardous when disturbed. Do not touch, brush, split, blow on, cut, sand, or grind a fibrous unknown. Habit is one field clue, so combine it with hardness, cleavage, streak, lustre, transparency, heft, magnetism, and geologic context.