amphibole

 
Pronunciation: /ˈamfɪbəʊl/

noun

[mass noun]
  • any of a class of rock-forming silicate or aluminosilicate minerals typically occurring as fibrous or columnar crystals: acid rocks consist mostly of quartz and feldspars, with a little mica or amphibole

Origin:

early 19th century: from French, from Latin amphibolus 'ambiguous' (because of the varied structure of these minerals), from Greek amphibolos, from amphi- 'both, on both sides' + ballein 'to throw'