amphibole
Concise Oxford English Dictionary © 2008 Oxford University Press:
amphibole /ˈamfɪbəʊl/
▶noun any of a class of rock-forming silicate or aluminosilicate minerals typically occurring as fibrous or columnar crystals.
– origin C19: from Fr., from L. amphibolus ‘ambiguous’ (because of the varied structure of the minerals).
'amphibole' also found in these Oxford entries:

