412 WULFENITE. 



examination of its optical properties, made 

 by Des Cioiseaux A?ith the polarising micro- 

 scope, to belong to Sillimanite, 



WuLFENiTE, Dana, Haidinger, Nicol. 

 Pyramidal : primary form the octahedron 

 •with, a square base. Occurs crystallized in 

 flat and in acute four - sided pyramids, 

 variously modified ; and in tabular crystals. 

 Also massive-granular. Colour generally 

 orange- or wax-yellow, passing into grey, 

 green or brown ; rarely aurora-red. Trans- 

 lucent. Lustre waxy or adamantine. Streak 

 white. Soft. Brittle. Fracture uneven or 

 imperfect-conchoidal. H, 3. S.G. 6-3 to 6-9, 



Fig. 468. 



Comp, Molybdate of lead, or Pb Mo = 

 oxide of lead 60*87, molybdic acid 39-13 = 

 100. 



Decrepitates strongly when heated, and 

 assumes a darker colour, which, however, 

 disappears on cooling; fuses to a yellow 

 mass. 



BB sinks into the charcoal, leaving glo- 

 bules of lead, while the charcoal becomes 

 impregnated with molybdenum arid molyb- 

 dide of lead. With carbonate of soda dis- 

 solves and sinks into the charcoal, leaving 

 globules. With borax dissolves easily ; the 

 glass formed in the outer flame is sfightl}'- 

 coloured ; that formed in the inner flame is 

 clear while hot, but in cooling, suddenly be- 

 comes dark and opaque. 



Dissolves in heated nitric acid, with se- 

 paration of yellowish-white nitrate of mo- 

 lybdic acid. Soluble in caustic potash, but 

 insoluble in Avater. 



Localities. — Foreign. Schwarzenbach, 

 Bleiberg, Windisch-Kappel, in Carinthia. 

 Rezbanya, in Hungary. Moldawa, in the 

 Bannat (in red crystals resembling chromate 

 of lead). Austria. Tyrol. Baden. Saxony. 

 Dauphiny. Zimapan in Mexico. Massa- 

 chusetts and Philadelphia, U.S. 



Name. After the Austrian metallurgist, 

 Wulfen. 



Brit. Mus., Case 39. 



WuNDERERDE. Wonder-eartli. See Tb- 



KATOLITE. 



WuNDERSALZ. See Glauber Salt. 



WiJREELERZ, Werner. See Pharmaco- 

 siderite. 



Wurfelspath, JFerner. See Anhyd- 

 rite. 



XANTHORTHITE. 



X. 



Xanthite, Mather, Thomson, Phillips. 

 A variety of Idocrase occurring in the form 

 of small rounded grains easily separable 

 from each other, and which appear under 

 the microscope to be imperfect crystals, 

 having a foliated texture. Colour' light 

 grej'ish or yellow. Translucent or trans- 

 parent. Lustre splendent, inclining to re- 

 sinous. H. easily crushed with the nail. 

 S.G. 3-2. 



Fig. 469. 



Locality/. Amity, in New York, U. S. 



Naine. From locvQos, yellow, in allusion to 

 its colour. 



Brit. Mus., Case 35. 



Xanthocone, Dana. Xanthokon, Breit- 

 hanpt, Nicol. Hexagonal. Occurs in very 

 thin six-sided tabular crystals, with alter- 

 nating oblique side-faces. Generally in 

 small reniform masses made np internally 

 of minute crystals. Colour dull red to clove- 

 brown. Orange-yellow at the edges by 

 transmitted light. Lustre adamantine. 

 Streak orange-yellow. Brittle. H. 2-25. 

 S.G. 5 to 5-2. 



Comp. Arsenio-sulphide of silver, or 

 (3Ag S + As2 S5) + 2(3 AgS + As2 S5) = silver 

 G6 2, arsenic 15-3, sulphur 18-6 = 100. 



BB on charcoal, gives off fumes of sul- 

 phur and arsenic, and leaves a grain of silver. 



Locality. The Himmelsfurst Mine, at 

 Freiberg, in Saxony. 



Name. From |oiv9o?, yellow, and y^ovis, 

 powder, in allusion to its yellow powder. 



Xanthophyllite, G. Rose. A variety 

 of Clintonite found in implanted globules, 

 and in columnar and lamellar individuals 

 which sometimes contain within thin, tabu- 

 lar, six-sided crystals. H. 45 to 6-5. S.G. 

 3-01 to 3-1. 



Comp. Combination of a silicate with 



aluminaf e of magnesia, or 2Mg Al + Ca Si. 



Locality. Schischimskian Mountains, 

 near Slatoust. in the Ural. 



Name. From |av6o?, yellow, and (pvXkov^ a 

 leaf, in allusion to its colour and lamellar 

 structure. 



Brit. Mus., Case 25. 



Xanthorthite. a yellowish variety of 



