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BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



of all edges, the solvent action having been greatest at the ends of 

 the trigonal axes where uneven faces have been produced. Shallow 

 rounded grooves replace the edges between (101) and (211) and a 

 rounding of the angles at the ends of the axes gives, in some cases, 

 an approximation to a cubic face. The etch facets would give no 

 measurable reflections, but their position shows that they are in part 

 trisoctahedrons and in part hexoctahedrons. The faces of both 

 (101) and (211) still retain a brilliant luster, but the former are 

 marked by beautifully symmetrical and sharp etch pits of rhombo- 

 hedral outline, their edges parallel to the dodecahedral edges of the 



crystal. The faces of (211) are 

 grooved quite deeply parallel to the 

 same edges. 



The garnets sometimes reach large 

 size. Livingston and Laney u found 

 a portion of a well-formed crystal IS 

 cm. in diameter on the dump of the 

 Arkansaw mine. 



A number of specimens from this 

 region which have been examined by 

 the writer are described as follows : 



A specimen from the Peacock claim 

 consists of fine large dark-brown crys- 

 tals up to 2 cm. in diameter embedded 

 in quartz. These are dodecahedrons 

 modified by narrow faces of the trapezohedron. They are asso- 

 ciated with a little hematite and bornite. When broken out 

 these crystals leave perfect molds in the quartz. Although firm and 

 lustrous on the outside, these crystals, when broken, are found to 

 be porous inside with the pores partly filled with chrysocolla. Under 

 the microscope the garnet is transparent, isotropic, and devoid of 

 notable zoning with an index of refraction above 1.82, estimated at 

 1.83. They are thus midway between grossularite and andradite in 

 composition. 



A specimen labeled "North drift, railroad tunnel," consists of 

 dense massive, fine-grained pure garnet of brown color and greasy 

 luster. It shows no suggestion of crystals, nor is there any other 

 mineral than garnet visible in the hand specimen. Under the micro- 

 scope the garnet is pale brown with a refractive index well above 

 1.82. It is isotropic. Numerous microscopic grains of calcite are 

 included in the garnet. 



Three specimens from the dump of the Queen mine consist of 

 massive garnet containing large spots which are evidently large 

 anhedral garnet crystals. These have cores up to 5 cm. maximum 



Fig. 76.— Garnet. Showing peculiar 

 etching. Seven Devils district. 

 After Palache. 



21 D. C. Livingston and F. B. Laney. Idaho Bur. Mines and Geol. Bull. 1, p. 63, 1920. 



