THE MINEBALS OF IDAHO 



315 



prisms of the mineral. Its refractive indices are e= 1.702, a; =1.708. 

 It is uniaxial and negative. For the most part the prisms show only 

 the faces of the prismatic zone and these deformed largely by con- 

 finement by adjacent crystals during growth. One minute cavity 

 filled with calcite showed several terminations and one of these was 



ir+? 



f- 



in 



Jb 



b 



mA 



Mm ffe^ 



/ 



ntf 



80 81 82 



Figs. 80-82.— 80, Vesuvianite. Brown crystal from Starlight mine, Wood River district, Blaine 

 County. 81, Vesuvianite. Showing form (6.12.5), Basin Group, Custer County. 82, Vesuvi- 

 anite. Showing form 174, Mackay, Custer County 



measured with sufficient accuracy to identify the forms. One of 

 these, approximating the indices (174) appears to be new but re- 

 quires confirmation. The habit is prismatic as shown in Figure 82. 

 The measurements are as follows: 



Measurements of vesuvianite Jrovi Mackay, Figure 82 



Specimens from the Basin group prospect which has been men- 

 tioned under hedenbcrgite and andradite and which is located near 

 the point where the Ketchum-Mackay road crosses the Trail Creek 



