THE AMERICAN MINERA]-OGIST, V0L. 53, JULY_AUGUST, 1968
EUCRYPTITE AND BIKITAITE FROM KING'S MOUNTAIN, NORTH CAROLINA
Pnrnn B. LrnvBns, DepartmentoJ Geology,Uniaersi,ty of Delaware, Newark, Delatpare C. S. Hunr.BUr, JR., Department of Geological S ci enc es, H arvar il U niv ers'ity, Combr.id. ge, M as s a chus etts Josueu A. Norow, U. S. National Museum, Wash'inglon,D. C. Ansrnect
vein fillings in the King's Mountain pegmatite yield good eucryptite crystals with a:13.4q[, c:9.016+0.007 A, a:c:l:0.6684 (X-ray), 1:0.6685 (morph.). Bititaite had a:8614, b:4.957, c 7.603+0.022 A, B:tt+" 19.3' (X-ray). chemicar anarysesyielded the formulas (LG.roNao.oo)Als.ss-Sro.o;Ozafor eucryptite and Li:.roAl:.ooSia.szOrz.1.95HrOfor bikitaite.
INrnooucrroN since its original descriptionby Brush and Dana (1880)from Branch- ville, connecticut, eucryptite has been reported from only three other localities.These are center strafford, New Hampshire; the Harding Mine, Dixon, New Mexico (Mrose, 1953); and Bikita, Rhodesia(Hurl- bfi, 1962).Bikitaite has beenreported only from Bikita (Hurlbut, i957). Both minerals have recently been found in lithium-rich pegmatites at King's n4ountain, North Carolina, where they occur sparingly as single crystals in seams. Although the eucryptite crystals are much smaller than thosefrom Bikita, they are free-growingand many are compretely bounded by crystal faces.The bikitaite, however,is deeplv etched and gives poor morphologicalmeasurements. chemical analysesshows that both mineralsare of nearly ideal composition.
OccunnBNcB A largeopencut mine in a pegmatiteswarm at King's Mountain, North carolina is operatedby the Foote Mineral company principalry for the recovery of spodumene. The mining operation and the geology of the locality have beendescribed by Kesler (1961).The pegmatites,as much as 2000 feet long and 200 feet thick, trending approximately north, and dipping steeply and irregularly both east and west, are intruded into thin- layered amphibolite and fine-grained mica schist. Diamond core drilling indicatesthat although the bodiesare approximately taburar, many are complexlyconnected at depthsof 100to 500feet. The pegmatitesshow almost no zoning,and are remarkably uniform in mineralogy and texture. occasional bodies of qtartz, a few tens of feet Iong, with associatedcoarse spodumene and microcline may represent 1202 EUCRYPTITEAND BIKITAITE I2O3
41 core segments.As a whole, the pegmatites are composedof about percent p.r..ni microcline and albite feldspar, 32 percent qvartz, 20 (Kesler' spodum"ne, 6 percent muscovite' and 1 percent other minerals tbOt;. ffre concentration of spodumeneis remarkable' Minor fractures in the pegmatites contain qtartz, albite, rhodochrosite, and a number of phosphatei, including apatite, vivianite and fairfieldite' amounts, In several of these fractures bikitaite has been found in small open most notably in the large pegmatite exposedon the west side of the min- pit, on the 7ih level, at about 6N section(Kesler, 1961,Fig' 2)' The jackstraws' ..ui o..rr* primarily in intergrowths of bladed crystals, like Albite, quuit", apatite, and fairfieldite are associatedwith it' Eucryptite in the crystals and narrow vein fillings were found in a single fracture section sarrrepegmatite body, on the 8th level of the pit, near the 1ON small (Kesler, 1961, Fig. 2). Associated minerals are albite, occasional associa- *p.uy, of white fairfieldite, and rare, sharp quartz crystals' The
Fro. 1. Eucryptite, King's Mountain North Carolina'
two tion of quartz and eucryptite, without bikitaite, indicates that these are minerali are co-stable' The veins of both eucryptite and bikitaite small and have yielded only a limited number of specimens'
Cnvsrnr,roceaPnv are as Ewcryptite.Although some of the free-growing eucryptite crystals only *.,.h u.5 mm in maximum dimension, most are smaller, measuring
ance. which Eight crystals were measuredon the two-circle goniometer all of showed the forms illustrated. in Figure 11 namely, c[0O01], m llO1O1, addition ispresenton r f10111,s [01121,I {10T4},y\tZSZl. In [11201 same some crystals. Although not as well developednor as uniform, these (Hurlbut' forms were al.o ,epoit"d on eucryptite crystals from Bikita 1204 LEAVT,NS,HURLBUT AND NZLEN
Bikitaite. The bikitaite crystals have a bradedhabit elongatedon [010] and range in length from lessthan one mm to over thirty mm. They are colorlessand transparentand bear a striking resemblanceto thosefrom the originallocality describedby Hurlbut (195g)in that the facesparallel to the length are of high quality but the ends are deeply etched.of ten
Tesrn 1. oprrcar. Pnopnntrrs a*o Spncu'tc Gpnv*v or Eucnvprtro ,q.ro Brxrrattn
Eucryptite Bikitaite