340 KRAMM— SERPENTINES OF THE CENTRAL [June 6, 



more resistant towards serpentinization. Partially altered fragments 

 of it were even found in nearly decomposed serpentine. 



Bronzite does not differ much from enstatite. Due to its higher 

 iron content it has higher interference colors, red of the first order 

 to blue of the second order, and is as a rule pleochroic from color- 

 less to a bright yellowish-green. 



Of the minor constituents picotitc is probably the most interest- 

 ing. Its grains are of considerable size and irregular in outline. 

 They were always found to be surrounded by black opaque masses 

 resembling either chromite or magnetite which also fill numerous 

 cracks traversing the crystal in all directions. (See Plate XXXV, 

 Fig. 4.) It is of a coffee-brown color, has a high relief and is 

 isotropic. 



It was possible to isolate some of these crystals by digesting with 

 hydrochloric acid and passing the residue through Thoulet solution, 

 then separating the picotite by hand. The crystals were .5 mm. in 

 diameter, glassy and hard enough to scratch quartz. 



The black coating was stripped off and subjected to the action 

 of a magnet. It was not magnetic and gave chromium reactions 

 before the blowpipe. It is therefore chromite. 



A series of slides made of specimens of serpentine varying 

 in degree of decomposition revealed interesting facts. As the 

 decomposition advances the outer opaque covering increases in 

 size while the picotite decreases. In a fairly decomposed serpentine 

 the picotite was still visible as a dot. In a much decomposed speci- 

 men, picotite disappears and only the irregular masses of chromite 

 remain. It seems therefore that chromite is secondary after picotite. 



Chromite itself was found as a primary constituent. It differs 

 from that considered as secondary in that the masses assume a more 

 geometrical outline. They are usually opaque, sometimes slightly 

 translucent with a reddish brown tint. 



Considerable quantities of chromite are known to occur in con- 

 nection with the serpentine, but are not utilized commercially at the 

 present time. Dr. Becker mentions chromic iron as occurring not 

 far from the Royal claim near Knoxville. It is of nodular form 

 in a seam which has been exposed by the weathering of the serpen- 

 tine. The writer has not been able to locate this. 



