SPODUMENE

This article appears in Volume V25, Page 712 of the Encyclopedia Britannica.

Encyclopedia Britannica - Main :: SOU-STE

SPODUMENE , a lithium-aluminium silicate belonging to the pyroxene group (see PYROXENE). It was named by B. J. d'Andrada e Sylva, in 'boo, from Gr. a'r63sec (ash-coloured), in allusion to its grey colour. Soon afterwards J. R. Ha-0y termed it tripltane, because it exhibited certain characteristics equally in three directions (Tpicbavifs, appearing three-fold). Spodumene crystallizes in the monoclinic system, the crystals having generally a prismatic habit and being often striated longitudinally. It has perfect prismatic cleavage, and imperfect cleavage parallel to the clinopinacoid, whilst a lamellar structure may be developed by parting along the orthopinacoid. The hardness is 6.5 to 7, and the specific gravity about 3.16. Though generally a dull

mineral

MINERAL

, some varieties of spodumene are so brightly coloured and transparent as to be valued as gem-stones. Such is the

emerald

EMERALD

-green hiddenite (q.v.) and the

lilac

LILAC

-coloured

kunzite

KUNZITE

(q.v.), whilst a yellow or yellowish-green spodumene found as pebbles in the state of Minas Geraes, in Brazil, resembles, when cut, some kinds of chrysoberyl. Common spodumene is used as a source of lithium in chemical pteparations.
Spodumene occurs in granite and crystalline schists. The

original

ORIGINAL

specimens came from the isle of Uto in Sodermanland, Sweden, but the finest examples are found in the United States, especially in

Massachusetts

MASSACHUSETTS (an Indian name, originally applied to a tribe of Indians)

, where Goshen, Sterling and Chester-field are well-known localities. Very fine specimens have been obtained from the Black Hills of S. Dakota. Some remarkable deposits containing spodumene were discovered many years ago at Branchville, Fairfield county, Connecticut, and the minerals which they yielded were exhaustively studied by Professor G. J. Brush and E. S.

Dana

. The spodumene occurred in large quantity, in a vein of albite-granite, associated with apatite, garnet, columbite,

pitchblende

PITCHBLENDE, or URANINITE

and other uranium minerals, together with several species of manganese phosphates, termed eosphorite, triploidite, dickinsonite, lithiophilite, natrophilite, reddingite, fairfieldite and fillowite. The spodumene, which has normally the

formula

LiAl (SiO3)2, becomes altered at Branchville to what has been called #-spodumene, which consists really of the

mineral

MINERAL

eucryptite (LiAlSiO4) and albite. Eucryptite was named by Brush and

Dana

from eu (well) and spurs-Os (concealed). Further alteration results in the formation of cymatolite, a mineral described by C. U. Shepard in 1867, but shown to be an intimate mechanical mixture of muscovite and albite. The final products of alteration of the spodumene may be muscovite, albite and microcline. The mineral discovered in 1817 in the granite of Killiney Hill, near Dublin, and described by T. Thomson as killinite, appears to be an altered spodumene. (F. W. R.*)

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