54 BULLETIN 118, UNITED STATES NATIONAL MUSEUM. 



It is used for paper weights, vases, and other ornaments, chiefly 

 as curiosities, and is worth little more than the cost of cutting. 

 Small faceted stones are sometimes cut from this mineral, but are 

 not sold commercially. 



LIST OF SPECIMENS. 

 UNITED STATES. 



New Hampshire. 

 Chatham, Carroll County: 



Brilliant, circular girdle; green-blue; 1.875 carats; 7.5 by 5 mm. Gift of 



Sumner Andrews No. 358 



Virginia. 

 Amelia Courthouse, Amelia County. 



Step-brilliant, rectangular girdle; very pale smoky brown; 5.047 carats; 



11 by 9 by 7 mm No. 357 



GADOLINITE. 



Composition. — Beryllium iron Yttrium orthosilicate, Be 2 FeY,0 2 

 (Si0 4 ) 2 . 



( 'i)/staUizaiio?i. — Monoclinic. 



Color. — Black. 



Luster. — Submetallic or brilliant vitreous; practically opaque 

 except in very thin splinters. 



Hardness. — 6.5; fairly durable. 



Specific gravity. — 4. 40 ±0.05. 



Optical properties. — Mean refractive index, 1.80; optically biaxial, 

 positive. 



Gadolinite can be distinguished from several minerals which it 

 resembles only by chemical tests. It is sometimes cut brilliant, 

 but its dark color prevents its extensive use as a precious stone, 

 and it is worth little more than the cost of cutting. 



LIST OF SPECIMENS. 

 UNITED STATES. 



Texas. 

 Burnet, Llano County: 



Brilliant, circular girdle; black, opaque; 8.56 carats; 13 by 8 mm. Isaac 

 Lea collection No. 587 



GARNET. 



There are three prominent groups of garnet with several subdi- 

 visions under each, many of these grading into each other. They are: 

 1. Aluminum garnet: 



Grossularite. — Lime-aluminum garnet. 



Pyrope. — Magnesium-aluminum garnet. 



Almandite and rhodolite. — Iron-aluminum garnet. 



Spessartite. — Manganese-aluminum garnet. 



