CONTRIBUTIONS TO MINERALOGY— SHANNON. 



445 



small cut which is largely filled in with leaves and soil, and the 

 relations of the lithia rich pegmatite are not shown. Surrounding 

 exposures consist of a normal granite-pegmatite of ordinary com- 

 position quite free from unusual accessory minerals. At least two 

 great dikes of normal pegmatite are exposed here. These are just 

 north of the Chatham-Haddam town line and propably represent 

 the continuation of the same pegmatite quarried at the famous Gil- 

 lette Haddam Neck quarry, which is not far distant in the line of 

 strike. The lithia-rich material forms a segregation, or, more proba- 

 bly, a slightly later complementary intrusion, in the main mass of the 

 granite pegmatite. The material removed from the cut consists 

 almost entirely of lepidolite and white quartz in nearly equal 

 amounts. Feldspar of the ordinary kind is entirely absent. The 

 lepidolite was mined for export for its lithia content, but most of 

 that extracted is still lying around the pit. The platy clevelandite 

 contains a few crystals of muscovite penetrated by crystals of 

 opaque green tourmaline and bordered by lepidolite in parallel 

 growth. The triplite occurs in irregular masses, which may reach 

 10 centimeters in diameter, ranging in color from flesh red to dark 

 brownish red. The cleavage is not pronounced and the material 

 resembles massive garnet. Intergrown intimately with the triplite 

 are muscovite and fine-grained deep-blue tourmaline, the last sur- 

 rounding the triplite in a crust and penetrating it along cracks and 

 appearing as though derived from the phosphate b}^ alteration. 

 Much of the triplite is granular and friable from mechanical dis- 

 integration. Some black oxide of manganese occurs as an alteration 

 product. The hardness of the mineral is around 3.5 ; specific gravity, 

 3.584. Upon analysis the results given in column I of the following 

 table were obtained. In column II is given the composition of the 

 triplite from Nevada.^ 



Hess and Hunt, Amer. Journ. Sci., vol. 36, p. 51, 1913. 



