Spodumene

Hand Specimen identification: Spodumene is typically found in pegmatites where it may form very large crystals. Prismatic cleavage, hardness, color, and association help identify it, but it may be difficult to tell from feldspar or scapolite. it often has the appearance of a log or of petrified wood.

Chemical Composition : LiAlSi2O6

Hardness : 6 1 2 to 7

Specific Gravity3.15

Cleavage/Fracture : two perfect prismatic {110}/uneven

Luster/Transparency : vitreous/transparent to translucent

Color : highly variable: colorless,white, gray, pink, green,yellow, purple, or tan

Streak : white

Optical Properties : Spodumene is similar to other clinopyroxenes in thin section. Its occurrence in pegmatites and its small extinction angle 120° to 26°2 help identify it. Biaxial 1+ 2, a = 1.65, b = 1.66, g = 1.67, d = 0.02, 2V = 60° to 80°.

Crystallography : Monoclinic, a = 9.52, b = 8.32, c = 5.25, b = 110.46°,Z = 4; space group C2/c; point group 2/m.

Habit : Prismatic crystals with well-developed {100} faces showing vertical striations are common. Crystals are often polysynthetically twinned and may be very large. In some pegmatites they are tens of meters long. Spodumene also occurs as cleavable masses.

Structure and composition : Spodumene is a pyroxene with structure similar to that of diopside. Minor Na substitutes for Li, Fe, Ca, Mn, Mg, and rare earths are also present in small amounts.

Occurrence and associations : Spodumene is found in granitic pegmatites, where it associates with K-feldspar, muscovite, quartz, tourmaline, beryl, and lepidolite.

Varieties : Hiddenite is a name given to emerald-green spodumene; kunzite to lilac/pink spodumene; and triphane to colorless or yellow spodumene.

Related Minerals : Spodumene is similar to other pyroxenes (see diopside). It is similar in composition to eucryptite, LiAlSiO4.

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