A PYRRHOTITIC PERIDOTITE 



135 



few of the larger and more massive grains are a deep grass green. 

 The interference colors between crossed nicols vary from greenish 

 yellow and dark gray in the light-green portions to very dark gray 

 in the deep green. The mineral is, in part at least, the product of horn- 

 blende decomposition. Calcite occurs in small, irregular crystals 

 and in aggregates of minute grains associated with chlorite, and 

 also as a few larger grains associated mainly with secondary hornblende. 



CALCULATION OF THE NORM FROM THE ANALYSIS 



Orthoclase . 

 Albite 



Anorthite . . 

 Corundum . 

 Rutile 



Hypersthene|^^gO^'Sia^J-56| 



Olivine ^f:0-SiO^ = 5-5i| 

 ( 2MgO-SiO.=25.48[ 



Nickel- and cobalt-bearing ) 



Pyrrhotite [ 



Magnetite 



Chalcopyrite 



Water 



Calcite 



P.O. 



, 22 .60 



. 30 . 99 I Femic 

 86.78 

 .22.50 ' 



. .10.00 



- 1-03 

 , . 4.02 



• 2.30 

 ■• -04 



100.16 



