372 PROCEEDINGS OF TUE NATIONAL MUSEUM. vol.58. 



resembling the green talc from the Tyrol. Hardness 2.5-3.0; specific 

 gravity 2.71; sensibly uniaxial, optically positive; color pale apple- 

 green; luster pearly on the cleavage face. Composition approxi- 

 mating to H4(]Mg,Fe)2 AlsSiOg. 



Tschermak ^ later assumed amesite to represent a fundamental end 

 member, and explained the constitution of the orthochlorites by 

 assuming them to be isomorphous mixtures of the amesite molecule 

 and the serpentine molecule. Considerable interest thus attaches to 

 the mineral which has been found only at this exhausted locality. 

 Since no ■ ther analysis of amesite than that of Pisani appears to 

 have been made and in order to determine the refractive indices on 

 analyzed material, the mineral has recently been analyzed again, 

 abundant material for investigation being supplied by a specimen 

 in the museum collection. This specimen is labeled "amesite and 

 diaspore, Chester, Mass." in the hand\mting of C. U. Shepard, 

 and the label bears also the words "Coll. by E. Messia," by which 

 is probably meant Macia, a French-Canadian, for many years fore- 

 man at the emery mine and an ardent collector of minerals. The 

 specimen consisted of a large flat mass of diaspore showing pale 

 grayish-pink cleavages several inches broad where broken and con- 

 taining small cavities filled with interlacing needle-like crystals of 

 diaspore. One side of the specimen is completely coated with a 

 layer of flat amesite crystals of a pale green color somewhat iron 

 stained. Scattered through the mass of the diaspore there are 

 variously oriented cr3"stals of amesite, large octahedrons of magnetite, 

 and crystals of dark red to black rutile. The amesite occurs in 

 tabular hexagonal crystals with dull prismatic faces. They reach 

 an extreme diameter of 1 cm. with a thickness of 3 to 5 mm. By 

 breaking up the diaspore, clean crystals were readily secured and 

 these, when ground, were used for analysis. The material was 

 perfectly homogeneous and free from impurities as shown by optical 

 study. 



The amesite has a uniform pale bluish-green color. The luster is 

 pearly to somewhat metallic on cleavage surfaces. In thick pieces 

 the mineral is translucent to almost opaque. Thin fragments are 

 transparent. The powder is white with a very faint tinge of green. 

 The mineral has a micaceous basal cleavage which, however, is not 

 nearly so perfect as in most crystallized chlorites. Laminae are rather 

 brittle and break in a manner suggesting a very imperfect prismatic 

 cleavage. The hardness is about 2.3, as it scratches gypsum readily, 

 but is scratched with great ease by calcito. The specific gravity as 

 determined on approximately 3 grams of coarse fragments in a 

 pygnometer is 2,77. 



iTheil, Sitzungsberichte Akad. Wien, vol. 99, 1890, pp. 174-207. 



