Acicular (crystal habit)

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

Minerals with an acicular habit include mesolite, natrolite,[1] malachite, gypsum, rutile, brochantite, bultfonteinite and dimethyltryptamine.[2]

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

References

  1. ↑ Hamilton, W.R. et al. (1974) The Hamlyn Guide to Minerals, Rocks and Fossils, London, Hamlyn, page 9.
  2. ↑ Bergin, Rolph. et al. (1968) Preliminary X-ray Crystallographic study of some psychoactive indole bases, Stockholm, Karolinska Institutet, page 1

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

http://www.mindat.org/

External links