Botriógeno (Mg Fe3+ OH (SO4)2 7H2O) de la mina Santa Elena, provincia de San Juan, Argentina.

Resumen

Botryogen (Mg Fe³⁺ OH (SO₄)₂ 7H₂O) from Santa Elena mine, San Juan Province, Argentina. Idiomorphic crystals of botryogen from Santa Elena mine, Calingasta, San Juan province, Argentina were studied. Botryogen (Mg Fe³⁺ OH (SO₄)₂ 7H₂O) is monoclinic, Prismatic class (2/m), space group P 2₁/n, a = 10.481(1), b = 17.828(1), c = 7.125(1) Å, b = 100°15’(LO), a:b:c = 0.5879:1:0.3997, cell volume 1310.10 ų, z = 4. Translucent crystals, transparent in small fragments, red orange color, streak pinkish yellow, vitreous luster, short prismatic crystals elongated along c, measuring till ½ cm. The predominant forms are a {100}, b {010}, m {110}, l {120}, d {101}, o {101}, p {011} and n {111}. The strogest peaks in the X-ray poder diagram are in Å: 8.88 (100), 4.076 (46), 5.121 (38), 6.301 (31), 3.752 (27), 3.012 (25), 2.741 (23), 3.191 (22), 3.509 (20). Botryogen is biaxial (+), a = 1.522(1), b = 1.530(1), g = 1.581(1), Na light, 2 V = 40°, X = b, Z Ù c = 10°, pleochroism X = yellowish white, Y = pale yellow, Z = reddish yellow, r > v strong, cleavages {010} perfect and {110} good, fragile, hardness 2 1/2, density 2.132 (meas.) and 2.106 (calc.) g/cm³.