Hornblende is a complex inosilicate series of minerals (ferrohornblende – magnesiohornblende). It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole.
|Color||Black to dark green or brown|
|Cleavage||Imperfect at 56° and 124°|
|Mohs scale hardness||5–6|
|Luster||Vitreous to dull|
|Streak||Pale gray, gray-white, white, colorless|
The general formula is (Ca,Na)2-3(Mg,Fe,Al)5(Al,Si)8O22(OH,F)2.
Some metals vary in their occurrence and magnitude:
Its planes of cleavage intersect at 56° and 124° angles. Hornblende is most often confused with the pyroxene series and biotite mica, which are also dark minerals found in granite and charnockite. Pyroxenes differ in their cleavage planes, which intersect at 87° and 93°.
It is the principal mineral of amphibolites. Very dark brown to black hornblendes that contain titanium are ordinarily called basaltic hornblende, from the fact that they are usually a constituent of basalt and related rocks. Hornblende alters easily to chlorite and epidote.
Other minerals in the hornblende series include:
- List of minerals – List of minerals for which there are articles on Wikipedia
- http://www.mindat.org/min-1519.html Mindat Ferrohornblende
- http://www.mindat.org/min-2524.html Mindat Magnesiohornblende
- "Hornblende Mineral | Uses and Properties".
- Phillips, M.W.; Draheim, J.E.; Popp, R.K.; Clowe, C.A.; Pinkerton, A.A. (1989). "Effects of oxidation-dehydrogenation in tschermakitic hornblende". American Mineralogist. 74: 764–773. Retrieved 30 December 2020.
- http://www.mindat.org/min-8789.html Mindat
- Handbook of Mineralogy
- Pough, Frederick H. (1976). A Field Guide To Rocks and Minerals (4 ed.). Boston: Houghton Mifflin. p. 249.