444 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 5S. 



It is possible by careful picking under a lens to free the mineral 

 for analysis from all visible impurities except quartz. A portion of 

 1 gram gave the following results: 



Analysis of tetrahedrite, Hypotheek Mine. 



Per cent. 



Quartz 13.57 



Sb 23. 03 



Fe 4. 41 



Cu 32. 38 



Zn 3.33 



Ag Trace 



As Trace 



Pb None 



Bi Trace 



S 22. 74 



Total 99. 46 



With impurities deducted the figures recalculated to 100 per cent^ 

 yield: 



Recalculated analysis of tetrahedrite. 



Sb 26.81 



Fe 5. 13 



Cu 37. 70 



Zn 3. 87 



8 26.49 



100. 00 



In view of its mode and place of occurrence the mineral is unique 

 in the absence of appreciable amounts of silver and arsenic, espe- 

 cially the latter, since arsenic is common as arsenopyrite in the same 

 vein. Owing to the small amount of material available it was im- 

 possible to prove the absence of zonal structure in the crystals. The 

 analysis consequently gives no basis for speculation as to the con- 

 stitution of the mineral. 



TRIPLITE FROM CHATHAM, CONNECTICUT. 



Some specimens of a brownish-red massive mineral supposed to 

 be triplite were shown the writer by Prof. William North Kice, 

 and with the aid of directions furnished by Professor Rice the locality 

 from which these specimens came was found and several specimens 

 were collected. Laboratory study of this mineral confirms the 

 original identification, the mineral being a normal triplite rather 

 low in iron, though not so low as one recently described by Hess 

 and Hunt. 



The mineral occurs imbedded in platy aggregates of the cleve- 

 landite variety of albite in a mass of pegmatitic material largely 

 consisting of quartz and lepidolite. These minerals came from a 



