University of California. 



[Vol. i. 



Number I was made by the writer in the Geological Laboratory 

 of the University of California, on selected crystal fragments, the 

 powder being dried at ioo° C. 



Number II was carried out at the University of Munich by Dr. 

 Palache on .7 gram of material obtained by crush ing and purifying 

 small crystals. 



The cause of the difference between the two analyses is not 

 known, and it is somewhat to be regretted that time does not per- 

 mit of a third analysis on the more abundant and better material 

 now at hand. However, as is shown in the foregoing table, either 

 of the two analyses would lead to the same formula, while the mean 

 of the two agrees quite closely with the theoretical composition. 

 The water is undoubtedly constitutional as the loss after raising the 

 powdered and dried mineral gradually up to a temperature of 225 C. 

 (the highest attainable with the apparatus at hand), and keeping it 

 so for over an hour, was only a little over o. 1 per cent. The follow- 

 ing is suggested as the probable structural formula: — 



GENERAL PHYSICAL PROPERTIES AND BLOWPIPE REACTIONS. 



The color of lawsonite resembles that of rather pale kyanite. 

 Small perfectly fresh crystals are generally clear and colorless, but 

 others, and especially the larger individuals, show a gray-blue color 

 that is unevenly distributed through their mass, much as in kyanite. 

 In weathering, the mineral suffers a loss of transparency and becomes 

 gray, or mottled with grayish and milky white patches. The luster 

 is vitreous, with a suggestion of greasiness. Its great hardness is 

 one of its most remarkable physical properties, and is about 8 

 in terms of Moh's scale. It scratches topaz readily, but is in turn 

 scratched by the latter mineral, and is apparently of the same degree 

 of hardness. It is markedly brittle. 



The specific gravity as determined by the chemical balance is 

 3.084. The powdered mineral as separated from the schist was 

 found to remain suspended in Thoulet solution cf 3.091 specific 

 gravity (Palache). 



(HOX, = AL 



o: 



(HO), = A. • 



>SiG\ 

 >Si0 3 



