Mitridatite from the San Luis granitic pegmatite, La Florida, Argentina.

GALLISKI, M. A., MÁRQUEZ ZAVALÍA, M. F., LOMNICZI DE UPTON, I., Y OYARZÁBAL, J. C.,

CANADIAN MINERALOGIST

Mineralogical Association of Canada

Lugar: Ottawa; Año: 1998 vol. 36 p. 395 - 397

0008-4476

An unusual coarse-grained sample of mitridatite from a granitic pegmatite is described. The mineral was found in threepieces of a fragmented nodule -10-20 cm, in the dumps of the San Luis mine, I-a Florida, Argentina. Similar nodules of primarytriphylite-lithiophilite altered to ferrisicklerite and dufr6nite are included in quartz from the core-margin association oftherare-element-enriched, spodumene-bearing granitic pegmatite. Mitridatite is very dark green, almost black, has a dull pale greenstreak and deep ruby red internal reflections. It has very good { 100} cleavage, vitreous luste!, a density of 3.221 g/cm3 and aMohs hardness of 5 to 5.5. The three strongest X-ray powder-diffraction lines [d in A(IXftftl)] are: 8.70(100)(200),2.901(80)(6^00a),n d 2.176(60)(800)T. he refined unit-cell parametersa re:d 17.505(1),b 19.327(3),c1 1.261(6)A , p 96.05(1)",y 3788(1) A:. Optically, mitridatite is transparent, with X pale green, almost colorless, )z= Z dark reddish brown, biaxial (-),2V -lO', a I.775(5), p 1.843(5), ^1 1.8aap), and very strong dispersion. The chemical composition gives: CaO 17.16, Mn2O3I.34,FerOr35.26,PzO532.26,HzO* 8.41, H2O 0.56, Rem. 4.51, which gives Cau.o,(II,0)6fFe3*8.6?Mno.33O6.r5(PO4)8.He12.O3.17The mitridatite is considered to have formed by hydrothermal replacement of primary triphylite.Keywords: mitridatite, nodule, granitic pegmatite, San Luis, Argentina.