284 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



In the contact-metamorphic copper deposits of the Alder Creek 

 district wollastonite occurs as scattered small grains in much of the 

 marble and garnet rock. Locally it forms a layer a foot or less in 

 width between granite porphyry and limestone. On the side of 

 the wollastonite away from the igneous rock is a persistent narrow 

 layer of pale blue marble bordered by a silicified zone of blue lime- 

 stone which grades outward through a foot or 18 inches into the 

 unaltered rock. The wollastonite rock is white, granular, and mas- 

 sive, and resembles the marble. 1 A specimen of such wollastonite 

 rock from the Case tunnel, Champion group, analyzed by W. C. 

 Wheeler gave the following results. 



Analysis of wollastonite rock, Mack ay 



(W. C. Wheeler, analyst) 

 Constituent Per cent 



Silica (Si0 2 ) 50. 47 



Alumina ( A1 2 3 ) • 45 



Ferric oxide (Fe 2 3 ) . 16 



Ferrous oxide (FeO) . 10 



Magnesia (MgO) 1. 17 



Lime (CaO) 45.99 



Carbon dioxide (C0 2 ) . 69 



Total 99. 03 



This analysis, computed in terms of mineral molecules gives the 

 following : 



Molecule Per cent 



Wollastonite 91. 24 



Diopside 5. 61 



Hedenbergite . 23 



Augite . 89 



Calcite 1. 75 



Quartz . 28 



Total 100.00 



ANTHOPHYLLITE (337) 



ASBESTUS 



Magnesium silicate, MgO.Si0 2 . Orthorhombic. 



Anthophyllite occurs in one locality in Idaho in very large masses 

 which constitute bodies of low grade " mass-fiber" asbestus similar 

 to that which is .mined at Sail Mountain, Ga. Several attempts 

 have been made to mine this material. The mineral probably oc- 

 curs in lesser amounts elsewhere in the State. Anthophyllite often 

 contains more or less ferrous iron and thus graduates toward the 

 similar orthorhombic iron amphibole described below under the 

 name ferroanthophyllite. 



i J. B. Umpleby. U. S. Oeol. Survey, Prof. Paper 97, pp. 55, 65, pi. 13, 1917. 



