Category: Aggregate habits
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Tabular/Blocky/Stubby – More elongated than equant, slightly longer than wide, flat tablet-shaped
Common examples include: feldspar, topaz, vanadinite
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Stellate – Star-like, radial aggregates radiating from a “star”-like point to produce gross spheres (crystals are not or weakly separated and have similar lengths)
Common examples include: pyrophyllite, aragonite, wavellite, “pyrite suns”
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Stalactitic – Forming as stalactites or stalagmites; cylindrical or cone-shaped. Their cross-sections often reveal a “concentric” pattern
Common examples include: calcite, chrysocolla, goethite, malachite
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Rosette/Lenticular – Platy, radiating rose-like aggregate (also lens shaped crystals)
Common examples include: gypsum, baryte, calcite
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Radial/Radiating/Divergent – Radiating outward from a central point without producing a star (crystals are generally separated and have different lengths)
Common examples include: atacamite, stibnite
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Pisolitic – Rounded concentric nodules often found in sedimentary rocks. Much larger than oolithic
Common examples include: bauxite, gibbsite
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Oolithic – Small circumferences or grains (commonly flattened) that resemble eggs
Common examples include: aragonite, calcite
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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 in what appears to be a hollowed out step lattice formation, as if someone had removed interior sections of the…
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Granular – Aggregates of diminute anhedral crystals in matrix or other surface
Common examples include: andradite, bornite, scheelite, quartz
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Foliated/Micaceous/Lamellar – Layered crystal structures, parting into thin sheets
Common examples include: muscovite, biotite, lepidolite, molybdenite
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Filiform or capillary – Hair-like or thread-like, extremely fine
Common examples include: many zeolites, byssolite, millerite, okenite
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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 common asbestiform mineral is chrysotile, commonly called “white asbestos“, a magnesium phyllosilicate part of the serpentine group. Other asbestiform minerals include riebeckite, an amphibole whose fibrous form is known…
