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, some varieties of spodumene are so brightly coloured and transparent as to be valued as gem-stones . Such is the emerald-green hiddenite (q.v.) and the lilac-coloured 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 specimens came from the isle of Uto in Sodermanland, Sweden, but the finest examples are found in the United States, especially in Massachusetts, 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 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 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 .