LoranditeTlAsS2
c 2001-2005 Mineral Data Publishing, version 1

Crystal Data: Monoclinic. Point Group: 2/m. Short prisms or tabular on {201}, pyramidal,
with many forms, striated parallel to [001]; needlelike to columnar, to 5 cm; granular.
Physical Properties:
Cleavage: Excellent on {100}, very good on {201}, good on{001}. Tenacity: Flexible, forming cleavage lamellae and fibers, with plastic deformation.
Hardness = 2–2.5 VHN = n.d. D(meas.) = 5.53 D(calc.) = 5.53
Optical Properties: Translucent to transparent. Color: Cochineal-red to carmine-red surface,commonly dark lead-gray, may be coated by an ocher-yellow powder. Streak: Cherry-red.
Luster: Metallic, adamantine.
Optical Class: Biaxial (+) (?). Pleochroism: Weak; Y = purple-red; Z = orange-red.
Orientation: X, Y' ⊥ {100}; Z = b. Dispersion: r > v, strong. n = > 2.72 (Li).
2V(meas.) = Large. Anisotropism: Strong.
R1 –R2 : (400) 28.8–30.6, (420) 28.7–30.7, (440) 28.6–30.8, (460) 28.4–30.9, (480) 28.2–31.2, (500)27.8–31.1, (520) 27.5–30.6, (540) 27.0–29.8, (560) 26.4–28.8, (580) 25.8–27.7, (600) 25.0–26.7, (620)
24.4–26.0, (640) 23.9–25.5, (660) 23.5–25.0, (680) 23.2–24.7, (700) 22.9–24.5
Cell Data: Space Group: P 21 /a. a = 12.296(9)β = 104.21(4)◦ Z = 8

b = 11.313(5)c = 6.114(1)X-ray Powder Pattern: Alšar, Macedonia.
3.59 (10), 2.88 (8), 2.97 (7), 1.867 (5), 1.484(5), 5.28 (4), 2.64 (4)Chemistry:TlAsS
rem.

(1)
59.76
22.30
18.99(2)58.7521.65
19.26
0.08

(3)
59.5
21.6
18.8(4)
59.46
21.87
18.67

Total 101.05
99.74
99.9
100.00(1–2) Alšar, Macedonia. (3) Carlin mine, Nevada, USA; by electron microprobe, average of fiveanalyses. (4) TlAsS2 .
Occurrence: Although rare, the most widespread thallium mineral; of hydrothermal origin,typically formed at relatively low temperatures.
Association: Stibnite, realgar, orpiment, cinnabar, vrabite, greigite, marcasite, pyrite,tetrahedrite, antimonian sphalerite, arsenic, barite.
Distribution: From Alšar (Allchar), near Rošden, Macedonia [TL]. At the Dzhizhikrut Sb–Hgdeposit, Tajikistan. From the Beshtau uranium deposit, near Pyatigorsk, northern Caucasus
Mountains, Russia. An ore mineral in the Lanmuchang Hg–Tl deposit, Guizhou Province,
China. At the Zarshuran gold deposit, near Takab, northestern Iran. From the Lengenbach
quarry, Binntal, Valais, Switzerland. In the USA, at the New Rambler Cu–Ni mine, Medicine
Bow Mountains, east of Encampment, Albany Co., Wyoming; in Nevada, from the Carlin mine,
50 km northwest of Elko, Lynn district, Eureka Co., in the Jerritt Canyon mines, Independence
Mountains district, Elko Co., and from the Getchell mine, Potosi district, Humboldt Co.; in theMercur gold deposit, Tooele Co., Utah.
Name:For Eötvös Lorand (1848–1919), physicist of Budapest, Hungary.

References: (1) Palache, C., H. Berman, and C. Frondel (1944) Dana’s system of mineralogy,(7th edition), v. I, 437–439. (2) Radtke, A.S., C.M. Taylor, R.C. Erd, and F.W. Dickson (1974)
Occurrence of lorandite, TlAsS2 , at the Carlin gold deposit, Nevada. Econ. Geol., 69, 121–174.
(3) Balić-Žunić, T., E. Makovicky, and Y. Moëlo (1995) Contributions to the crystal chemistry ofthallium sulfosalts III. The crystal structure of lorandite (TlAsS2 ) and its relation to weissbergite(TlSbS2 ). Neues Jahrb. Mineral., Abh., 168, 213–235. (4) Vlasov, K.A., Ed. (1966) Mineralogy ofrare elements, v. II, 592–597. (5) Berry, L.G. and R.M. Thompson (1962) X-ray powder data forthe ore minerals. Geol. Soc. Amer. Mem. 85, 146–147.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted inany form or by any means, electronic, mechanical, photocopying, recording, or otherwise without the prior written
permission of Mineral Data Publishing.