Hornblende

Hornblende
Hornblende crystal (dark green) about 35 mm long, with apatite (white)
General
CategorySilicate mineral
Formula
(repeating unit)
Ca2(Mg,Fe,Al)5(Al,Si)8O22(OH)2
IMA symbolHbl[1]
Crystal systemMonoclinic
Space groupC2/m
Identification
ColorBlack to dark green or brown
Crystal habitHexagonal/granular
CleavageImperfect at 56° and 124°
FractureUneven
Mohs scale hardness5–6
LusterVitreous to dull
StreakPale gray, gray-white,[2][3] white, colorless[4]
Specific gravity2.9
PleochroismStrong
References[5]

Hornblende is a complex inosilicate series of minerals.[6] 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. Hornblende minerals are common in igneous and metamorphic rocks.

The general formula is (Ca,Na)2−3(Mg,Fe,Al)5(Al,Si)8O22(OH,F)2.

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Ferrohornblende, Mindat.org
  3. ^ Magnesiohornblende, Mindat.org
  4. ^ "Hornblende Mineral | Uses and Properties".
  5. ^ 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.
  6. ^ Hornblende Root Name Group, Mindat.org