208 METALS. 



Bodcnite is a cerium ore, resembling orthite. From Boden ia 



Baxony. 



PYROCHLORE. 



In small octahedrons, with a cleavage parallel to the face? 

 1 of the octahedron sometimes dis* 2 



tinct. 



Color yellow to brown. Sub* 

 transparent to opake. Luster, 

 vitreous inclining to resinous. 

 H=5. Gr=3«8— 4'3. 



Composition : essentially co- 

 lumbic acid, with oxyds of cerium, thorium, and lime. Ti- 

 tanic acid sometimes replaces part of the columbic acid. 

 Fuses with very great difficulty before the blowpipe. 



The microlite of Prof. Shepard appears to be pyrochlore. 

 Dif. The color, difficult fusibility and colored streak 

 distinguish this species from others crystallizing in octahe- 

 drons. It is much softer than spinel. 



Obs. Occurs in syenite in Norway, and also in Siberia. 

 In the United States it is found in minute octahedrons at the 

 Chesterfield albite vein, Mass. 



The following species contain yttrium or cerium as a char- 

 acteristic ingredient : — 



Xenotime is a phosphate of yttria, having a yellowish-brown color 

 pale brown streak, opaque, and resinous in luster. Crystals square prisms, 

 with perfect lateral cleavage. H=s=4 — 5. Gr==4'6. Infusible alone 

 before the blowpipe ; insoluble in acids. From Lindesnaes, Norway. 



Gadolinite has a black or greenish-black color, resinous or subvitre- 

 ous luster, greenish-gray streak. Crystalline form an oblique rhombic 

 prism, with no distinct cleavage. H=6'5 — 7. Gr.=4*l--4 - 4. Con- 

 sists mainly of silica, yttria, glucina, and protoxyd of iron, with also the 

 recently discovered oxyd of lanthanum. From Fahlun and Ytterby, 

 Sweden ; also from Norway and Greenland. 



Fergusonite is a columbate of yttria, crystallizing in secondaries to a 

 square prism. Color brownish-black ; luster dull, but brilliantly vitre- 

 ous on a surface of fracture. Infusible before the blowpipe but lo&es its 

 color. From' Cape Farewell, Greenland. 



Yttro-tantalite is a tantalateof yttria containing half as much yttria 

 as the preceding. There are three varieties, the black, the yellow, and 

 the brown or dark-colored. They are infusible. From Ytterby, Swe- 

 den, and at Broddbo and Finbo, near Fahlun. 



Eaxenite is a columbate of yttria with some titanic acid and oxyd of 

 uranium. Massive. Color brownish-black. Streak powder redcisb* 

 brown. Infusible. From Norway. 



What is the appearance and composition of pyrochlore 1 



