Botryoidal

Combination of botryoidal chrysocolla with smaller balls of sparkly malachite

A botryoidal texture or mineral habit is one in which the mineral has a globular external form resembling a bunch of grapes as derived from the Greek botruoeidēs.[1] This is a common form for many minerals particularly hematite where it is the classically recognized shape. It is also a common form of goethite, smithsonite, fluorite and malachite. This includes chrysocolla.

Each sphere (grape) in a botryoidal mineral is smaller than that of a reniform mineral, and much smaller than that of a mamillary mineral. Botryoidal minerals form when many nearby nuclei, specks of sand, dust, or other particles, are present. Acicular or fibrous crystals grow radially around the nuclei at the same rate, appearing as spheres. Eventually, these spheres abut or overlap with those that are nearby. These nearby spheres are then fused together to form the botryoidal cluster.

References

  1. ↑ https://en.oxforddictionaries.com/definition/botryoidal
  • Klein, Cornelis and Cornelius S. Hurlbut, Jr.; 1985; Manual of Mineralogy; Wiley; 20th ed.; p 199; ISBN 0-471-80580-7
  • http://www.minerals.net/mineral_glossary/botryoidal.aspx
  • http://www.britannica.com/EBchecked/topic/75161/botryoidal-texture
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