Mineral Factbook

Muscovite

KAl2(Si3Al)O10(OH)2IMA symbol: Msapproved

Muscovite is a silicate mineral with the formula KAl2(Si3Al)O10(OH)2, crystallizing in the monoclinic system. It has a Mohs hardness of 2-2.5, typically colorless, brown, gray or green in color, with a pearly or silky luster, a specific gravity of 2.76-3. Its streak is red.

Photos

Muscovite specimen photo
Jonas Börje Lundin · CC BY-SA 4.0 · Commons
Muscovite specimen photo
Jonas Börje Lundin · CC BY-SA 4.0 · Commons
Muscovite specimen photo
CarlesMillan · CC BY-SA 3.0 · Commons
Muscovite specimen photo
P. Fernandes (Trebaruna) · CC BY 3.0 · Commons

Crystallography

Crystal systemmonoclinic crystal systemWikidata (CC0)
Space groupC 1 2/c 1
Cell (Å, °)a = 5.1969, b = 9.0138, c = 20.0835; α = 90, β = 95.763, γ = 90
Cell volume936.033 ų, Z = 4
Axial ratios0.5765:1:2.2281calculated from COD 9017156
Source structureCOD 9017156 (The Canadian Mineralogist, 2013) — 1 of 35 structures

Powder X-ray diffraction (calculated)

2θ (degrees, Cu Kα1)I/I₀ (max 100)
d (Å)2.564.469.9913.4922.993.202
I/I₀10097.29284.884.380.5

xrd-v1: CuKa1 1.5406A, 2theta 5-90, top10, Imax=100, no DW/PO. Computed from COD 9017156; idealized occupancies, no preferred orientation.

Physical properties

Density (calculated)2.812 g/cm³calculated from COD 9017156
Hardness (Mohs)
2-2.5single sourceDana, System of Mineralogy, 6th ed. (1892)
Specific gravity
2.76-3 g/cm3corroboratedDana, System of Mineralogy, 6th ed. (1892)
Color
brown, colorless, gray, green, red, rose, violet, yellowsingle sourceDana, System of Mineralogy, 6th ed. (1892)
Streak
whitesingle sourceWikidata (CC0)
redsingle sourceDana, System of Mineralogy, 6th ed. (1892)
Luster
pearly, silky, vitreoussingle sourceDana, System of Mineralogy, 6th ed. (1892)

Chemistry (calculated)

Molecular weight398.31 g/molcalculated from the IMA formula
Composition (wt%)K 9.82%, Al 20.32%, Si 21.15%, O 48.2%, H 0.51%

Classification

Nickel-Strunz (9th)9.EC.15Wikidata (CC0)
Dana (8th)71.2.2a.1Wikidata (CC0)