52 



THOMAS STERRY HUNT ON A NATURAL SYSTEM IN 



resembles the more basic silicate of glnciua, irou aud zinc, danalite, belougiug to the same 

 tribe. AVith these are also placed leucophauite, which is interesting as being a fluoriferous 

 silicate of glucina, lime aud soda, having the same atomic ratio for its bases as serpentine 

 and chrysotile. Among bisilicates we find, in this tribe, wollastonite, a simple lime- 

 silicate, and tsehetfkinite, a titauosilicate of lime with cerous and ferrous oxyds. All of 

 the silicates of this tribe are decomposed by acids with pectisation. 



Tribe 3. — Protadamantoids. 



§ G4. We next proceed to note the adamantoid protosilicates or Protadamantoids, 

 closely connected with the Protospathoids, but distinguished from them l)y a more 

 condensed molecule and a greater resistance to acids. First in order comes the lluo- 

 riferous magnesian silicate, chondrodite, then the double silicate of lime and magnesia, 

 mouticellite, (which, from its recorded specific gravity, would seem to be a denser silicate. 



IV. 



Tribe 3. Protadamantoid. 



isomeric with the spathoid batrachite,) and the chrysolites, belonging to a more condensed 

 type than either. The genus, chrysolite, includes not only the ordinary more or less ferrous 

 species, but forsterite on the one hand, and hortouolite and fa3'alite on the other. To this 

 succeed the two gluciuic species, phenacite and bertrandite, the former of which is the 

 most highly condensed protadamantoid known, while the latter is remarkable for contain- 

 ing a portion of water. Next in order comes the maugauesian species, rhodonite, together 

 with the amphiboles and pyroxenes, two important genera, or rather families, which (with 

 the apparent exception of certain amphiboles having the atomic ratio of bases to silica of 



