PSEUDOMORPHOUS MINERALS OF NEW YORK. 243 



Schoharie, the sulphate of baryta often has admixtures of car- 

 bonate of sti-ontia and carbonate of lime, and several new spe- 

 cies have been proposed, in which diflerences in chemical com- 

 position are chiefly relied on as distinctive characters. Such are 

 believed to be the Calstron-haryte of Shepard, and the Em- 

 monsite of Thomson. I have also analyzed a mineral from that 

 locality, which has the same, or nearly the same crystalline form 

 as sulphate of baryta, but which is a mixture of the sulphates 

 of strontia and baryta, with twelve or thirteen per cent, of 

 carbonate of lime. There seems to be here a series of replace- 

 ments and mixtures, which renders it extremely hazardous to 

 propose new species from mere differences in chemical compo- 

 sition. 



Changes in Minerals containing Magnesia. 



In Phillipstown, in the county of Putnam, there is a bed ' of 

 white limestone, which contains serpentine in considerable 

 abundance. This mineral here presents several varieties, which 

 may be traced to foreign admixture. One variety has a con- 

 choidal fracture, exhibits various shades of gi'een and yellow, 

 and is found in small rounded masses. Another has a dark 

 gi'een color, is very hard and compact, has a slaty structure, 

 and sometimes breaks into rhomboidal prisms. A thkd variety 

 is also slaty, has a gi*eenish white color, is harder than either of 

 the preceding, and is fusible upon thin edges, by the blow-pipe. 

 It is evident, from an inspection of the locality, that all these 

 belong to the same species, and yet, in hand specimens, they 

 might "well be considered as distinct. The slaty and altered 

 appearances which the serpentine exhibits, is due to the ad- 

 mixture of pyroxene or tremolite, or both, minerals which are 

 here found in sufficient abundance. 



I may also add in this place, that from an attentive exami- 

 nation of numerous localities, I have little doubt of the identity 

 of the several minerals, which have passed under the names of 

 marmolite, kerolite, magnesite, retinalite, and Deweylite. They 

 are all serpentine, more or less altered by the intrusion of 

 foreign substances. The marmolite of Hoboken and Staten 



