Oolithic – Small circumferences or grains (commonly flattened) that resemble eggs
Common examples include: aragonite, calcite
Hopper – Like cubic, but outer portions of cubes grow faster than inner portions creating a concavity
Common examples include: halite, calcite, synthetic bismuth A hopper crystal is a form of crystal, the shape of which resembles that of a pyramidal hopper container. The edges of hopper crystals are fully developed, but the interior spaces are not filled in. This results i
Granular – Aggregates of diminute anhedral crystals in matrix or other surface
Common examples include: andradite, bornite, scheelite, quartz
Foliated/Micaceous/Lamellar – Layered crystal structures, parting into thin sheets
Common examples include: muscovite, biotite, lepidolite, molybdenite
Filiform or capillary – Hair-like or thread-like, extremely fine
Common examples include: many zeolites, byssolite, millerite, okenite
Fibrous (including asbestiform) – Extremely slender prisms, muscle-like fibers
Common examples include: serpentine group, actinolite, kyanite, gypsum, nitratine, tremolite (i.e. asbestos) Asbestiform is a crystal habit. It describes a mineral that grows in a fibrous aggregate of high tensile strength, flexible, long, and thin crystals that readily separate. The most
Druse, encrustation – Aggregate of crystals coating a surface or cavity, usually found in geodes
Common examples: azurite, celestine, calcite, uvarovite, malachite, quartz In geology, druse refers to a coating of fine crystals on a rock fracture surface or vein or within a vug or geode. See also References
Dendritic, Arborescent – Tree-like, branching in one or more direction from central point
Common examples include: romanechite, magnesite, native copper
Coxcomb – Aggregated flaky or tabular crystals closely spaced.
Common examples include: barite, marcasite
Concentric – Circular ring aggregates around a center
This habit is found in cross-sections from reniform/mamillary habits, and also from elongated stalactites of amethyst (quartz), malachites, rhodocrosite, and others Common examples include: quartz, malachite, rhodocrosite
Columnar – Similar to bladed and radial: Long, slender prisms often with parallel growth
Common examples: calcite, gypsum/selenite
Bladed – Blade-like ends, slender and somewhat flattened
Common examples: quartz, stilbite, kyanite
Acicular – Needle-like, slender and/or tapered
Acicular, in mineralogy, refers to a crystal habit composed of slender, needle-like crystals. Crystals with this habit tend to be fragile. Complete, undamaged acicular specimens are uncommon. The term “acicular” derives from the Late Latin “aciculaR