Acicular

Natrolite showing acicular crystal habit

Acicular, in mineralogy, refers to a crystal habit composed of a radiating mass of slender, needle-like crystals. Minerals with this habit tend to be fragile and complete, undamaged specimens can be uncommon.

Examples

Some minerals with an acicular habit include mesolite, natrolite,^[1] malachite, gypsum, rutile and brochantite.

Differences from other habits

Some minerals like creedite form prismatic crystals that appear to be acicular, but are instead prismatic in a bladelike form; these can be told apart by the fact that all prismatic crystals are less sharp, sometimes are tipped with a pyramidal shape, and keep a standard cross-section shape with straight edges. Acicular crystals differ from fibrous crystals in their thickness; crystals with a fibrous habit are much thinner, sometimes to the point of being flexible like hair, while acicular crystals are thicker and rigid.

See also

Needle-shaped acicular millerite crystals on white quartz

• Zeolite

References

http://www.galleries.com/minerals/property/habits.htm#acicular

http://www.mindat.org/

External links

• "Skeletal microstructure of Galaxea fascicularis exsert septa: a high-resolution SEM study", Biological Bulletin

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