Mechanical

Density: Gr./Cu. Cm. 2.6-3.2
Lb./Cu. Ft. 160-200
Hardness, Mohs 2.0-3.2
Cleavage Basal, Eminent
Crystal Structure Monoclinic
Max. Temperature with no decomposition 400-500C
Specific heat (25C) .206-.209
Thermal Conductivity perpendicular to cleavage: Cal./Sq. Cm./Sec./Cm./C 16x10-4
B.T.U./Sq. Ft./Hr./I.F 4.6
Coefficient of expansion per C perpendicular to cleavage:   20 - 100 C 15x10-6 - 25x10-6
100 - 300 C 15x10-6 - 25x10-6
300 - 600 C 16x10-6 - 36x10-6
Coefficient of expansion per C parallel to cleavage:     0 - 200 C    8x10-6 - 9x10-6
200 - 500 C 10x10-6 - 12x10-6
Tensile strength, P.S.I. 37,000 - 43,000
Modulus of elasticity 25x106

Electrical

Dielectric Constant 6.5 - 9
Dielectric Strength (highest qualities 1-3 mils thick), volts/Mil. 6,000 - 3,000
Power Factor at 25C (77F) (highest qualities), percent:       60 cycles 0.08 - 0.09
1 megacycle 0.01 - 0.02
Resistivity, Ohm-Cm. 1012 - 1015

Optical

Optic axial angle (2V) degrees 38 - 47
Orientation of optic plane to plane of symmetry Perpendicular
Indexes of refraction Alfa 1.552 - 1.570
1.582 - 1.607
Char  1.588 - 1.611
*Muscovite
*Compiled by U.S. Bureau of Mines