G. F. Runzs—Minerals From Stoneham, Me. 213 
The color in these rough crystals is more decided than in the 
finer ones and isa light shade of either green, yellow or blue. 
The specific gravity of the transparent material is 3°54, and the 
hardness the same as that of the yellow topaz from Oura Preto 
eoemesly Villa Rica), Brazil. 
@ following forms have been observed : 
0, +4; prisms i & i-§, ‘-2, i-3, i-d; macrodomes }-i, 2-2; brachydomes 2-%, 4-1; 
Pyramids 4,4 4 1, 2; 4-2, +3, > 
Many of the crystals exhibit a pearly and at times an opa- 
lescent luster when viewed in the direction of the plane O, 
apart from the iridescence produced by fracture and cleavage. 
A specimen of this topaz was sent to Professor J. W. Mallet 
for examination. In a letter to the writer, dated July 27, 
1883, he says: 7 
oer, Bradbury, of Petersburg, Va., has made what he 
himself believes to be a good and accurate analysis, and has ob- 
tained the following remarkable results : é 
Aluminum rege Aas 3 
SEDON co hae ee 14°64 
Fluorine eg 29°21 
Oxygen 28°56 
99°55 
Counting the oxygen as the sum of that equivalent to the alumi- 
num and Sie: ess one atom of oxygen for two of fluorine 
found. These figures lead to the usual formula for topaz, 
but presents the sf 
remarkable anomaly that, instead of one-half of the oxygen 
