Question

Write the physical properties and importance of (i) augite (ii) hornblende

Answer 1

Hornblende is a complex inosilicate series of minerals (ferrohornblende – magnesiohornblende).[4] 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

Hornblende crystal (dark green) about 35 mm long, with apatite (white)

GeneralCategorySilicate mineralFormula
(repeating unit)Ca2(Mg, Fe, Al)5 (Al, Si)8O22(OH)2Crystal systemMonoclinic unknown space groupIdentificationColorBlack to dark green or brownCrystal habitHexagonal/granularCleavageImperfect at 56° and 124°FractureUnevenMohs scale hardness5–6LusterVitreous to dullStreakPale gray, gray-white,[1][2] white, colorless[3]Specific gravity2.9PleochroismStrong

Hornblende is an isomorphous mixture of three molecules; a calcium-iron-magnesiumsilicate, an aluminium-iron-magnesium silicate, and an iron-magnesium silicate.

The general formula can be given as (Ca,Na)2–3(Mg,Fe,Al)5(Al,Si)8O22(OH,F)2