Acicular (crystal habit)

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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[edit]

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

Differences from other habits[edit]

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[edit]

Needle-shaped acicular millerite crystals on white quartz

References[edit]

  1. ^ Hamilton, W.R. et al. (1974) The Hamlyn Guide to Minerals, Rocks and Fossils, London, Hamlyn, page 9.

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

http://www.mindat.org/

External links[edit]