Coefficients of Expansion and Densities of Optical Materials

Coefficient of Expansion
(×10⁻⁶ per ^°C)

Density
(lbs/cubic in.)

Aluminum

23.8

0.10

Brass (cast)

18.8

0.30

Carbon (diamond)

  1.2

0.25

Carbon (graphite)

  7.9

—

Copper

16.2

0.32

Germanium

  5.9

0.20

Glass (optical)

    maximum

15.0

0.22

    minimum

  4.0

0.08

    average

  8.0

0.11

Gold

14.0

0.70

Invar (36% Ni)

  0.9

0.30

Iron (cast)

10.0

0.27

Iron steel

13.2

0.28

Lead

28.0

0.41

Magnesium (cast)

27.0

0.06

Nickel

12.6

0.32

Plastics (optical)

65.0

0.04

Platinum

  9.0

0.77

Pyrex

  3.5

0.10

Quartz, fused

  0.6

0.08

Rubber (hard)

80.0

0.04

Silicon

2.33

0.08

Steel, stainless

12.0

0.30

Zinc sulfide (ZnS)

  7.9

0.15

Zinc selenide (ZnSe)

  7.6

0.20