SILICA. 
281 
Two miles north of Rye, is another and more abundant locality of the same mineral. It 
usually occurs in thin and very brittle plates of a white or light green colour. It has a some¬ 
what resinous lustre, and is translucent on thin edges. Sometimes, however, it appears to 
be largely intermixed with true serpentine, and forms masses of considerable size. These 
masses are usually made up of angular fragments, separated from each other by thin seams 
of hydrate and carbonate of magnesia, the hydrate being in small pearly imperfect crystals 
or plates, and the carbonate in a white powder, probably resulting from the action of the 
atmosphere upon the hydrate. 
According to my analysis of the green and compact portion, it contains 
Silica,. 40.50 
Magnesia,. 38.00 
Water,. 21.00 
Oxide of iron,. traces. 
This mineral, therefore, is quite similar in composition to that from Staten island. 
The so called Agalmatolite, from Warwick in Orange county, is probably identical with 
this species ; while the Pseudolite, (or the pseudomorplis , as they have been called, of horn¬ 
blende, scapolite and spinelle,) which is supposed to belong to kerolite or magnesite, includes 
several mixtures of the minerals whose crystalline forms they represent, and some of the mine¬ 
ral matters which serpentine and magnesite are usually found to contain. 
The general similarity in the chemical composition of the several minerals just noticed, 
sufficiently indicates their identity. The differences in some of the external characters may 
easily be accounted for, when we reflect upon the usual associates of these minerals, and the 
ease with which these associates are at least partly decomposed. Perhaps the most widely 
different variety is that of a dark green colour found at Stony point, and which uniformly 
contains from ten to twelve per cent, of oxide of iron. If I were to suggest a name for this 
mineral, it would be that of Rocklandite. 
CHONDRODITE. 
[From the Greek %ov<5pos, a grain; in allusion to its mode of occurrence.] 
Chondrodite. Berzelius and Thomson. — Brucite. Gibbs , Ckaveland and Shepard. — Condrodite. Hauy , Phil¬ 
lips and Beudant. — Hemiprismatic Chrysolite. Jameson. — Hemiprismatischer Chrysolith. Mohs. — Maclu- 
rite. Seybert. 
Description. Colour various shades of yellow, brown and red. 
It occurs massive and in small grains. According to Haiiy, it 
cleaves parallel to the faces of a right oblique prism (Fig. 190), 
the greater angle of which is 112° 12'; but Cleaveland describes 
it as occurring in rhombic prisms of 124° and 56°, with dihedral 
terminations. Fracture imperfectly conchoidal. Lustre vitreous 
to resinous. Translucent. Hardness 6.5. Specific gravity from 
36 
Min. — Part II. 
