Category: Aggregate habits
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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
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Dendritic, Arborescent – Tree-like, branching in one or more direction from central point
Common examples include: romanechite, magnesite, native copper
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Coxcomb – Aggregated flaky or tabular crystals closely spaced.
Common examples include: barite, marcasite
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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
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Columnar – Similar to bladed and radial: Long, slender prisms often with parallel growth
Common examples: calcite, gypsum/selenite
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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 “acicula” meaning “little needle”. Strictly speaking, the word refers to a growth habit that is slender and tapering to a point. Prismatic crystals are not acicular; however,…
