134 Hillebrand and Ransome — Carnotite and Associated 



For comparison, the latest analysis of roscoelite from Placer- 

 ville, Calif., is given a place in the above table. Peculiar, 

 though unimportant, is the coincidence that the only two 

 known localities for this mineral should bear the name Placer- 

 ville. 



II. Green Sandstone Colored by Chromium. 



Other sandstones much brighter green than the vanadiferous 

 one were observed and collected by Dr. Ransome, both at 

 Placerville and 60 miles distant in Sinbad Yalley. The color 

 suggested a salt of copper as its cause, but analysis showed it 

 to be due to chromium. Time has failed for an examination 

 as to the nature of this coloring body. It is very difficultly 

 soluble, thus presenting greater hindrance to analysis than was 

 the case with the vanadium compound. It would be interest- 

 ing to find it to be a micaceous mineral analogous to the one 

 just described. Under the microscope it presents a chloritic 

 appearance (Ransome). If opportunity offers, the problem of 

 its nature may yet be attacked. 



In still another greenish sandstone from the west bank of 

 the Dolores Biver, near the mouth of La Sal Creek, analysis 

 failed to show either vanadium or chromium. 



III. The Carnotite Ores. 



Optical Examination. — Dr. Geo. P. Merrill has kindly sub- 

 mitted the following notes. 



" The carnotite powder appears under the microscope in the 

 form of exceedingly minute dust-like particles, without crystal 

 outlines and acting so faintly on polarized light as to at first 

 seem almost amorphous. Much of the matter appears merely 

 as a fine brownish clay, stained yellow by an amorphous pig- 

 ment, but occasionally a well-defined fragment of a light yel- 

 low, translucent mineral is met with which doubtless represents 

 the vanadium compound in its condition of ideal purity. 



Working over a considerable amount of the powder, I have 

 found occasional clusters of this yellow mineral in the form of 

 flattened radiating crystals with pyramidal terminations which 

 are without evident pleochroism, polarize only in dull colors, 

 and give extinctions always parallel to the axis of elongation. 

 These are so minute (not over 0*25 mm in length) and so thin 

 that I have never been able to find a crystal so oriented as to 

 give an opportunity of determining its exact character, and I 

 can only say that the general shape is such as to suggest a 

 hexagonal mineral, though this is by no means certain." 



Chemical Examination of the Carnotite Ores. — The chemical 

 problems involved in the analysis of the carnotite ores were 

 peculiarly intricate. Ideal material was quite unobtainable 



