SILICA. 283 



St. Lawrence County. Chondrodilc is found in wliiic limestone on the bank of Laidlavr 

 lake, in ihc town of Ilossie, about two nules north of the village of Oxbow. It is in the form 

 of small yellow grains, but it is not abundant. 



Again, two miles from Somcrville, in the same town, it occurs nearly of the same colour, 

 associated with light blue spinelle. It is near the locality of buff serpentine and mica. 



With the above exceptions, I know of no localities of this mineral in Northern New-York. 

 It has, however, long been placed among the minerals of Rogers' rock, but I have never met 

 with it at that locality. 



In New- Jersey, chondrodite has been found abundantly in the county of Sussex, which 

 adjoins that of Orange, N. Y. 



BOLTONITE. 



[From Bolton in Massachusetts, where it was first found.] 



Boltonilc. Shrpard and Dana. 



Description. This mineral, which, however, is still a doubtful one, has heretofore been 

 found only massive. Its fracture is coarsely granular. Colour bluish grey, yellowish grey, 

 wax-yellow to yellowish white. Streak while. Cleavage pretty distinct in one direction ; in 

 two others oblique to the first, indistinct, but atTording indications of a doubly oblique prism 

 for the primary form. Fracture uneven. Lustre vitreous. Transparent to translucent. Hard- 

 ness from 5.0 to 6.0. Specific gravity from 2 . 80 to 2 . 90. Before the blowpipe, it becomes 

 white and transparent, but is infusible ; with borax, it yields a transparent glass. 



This mineral was first found at Bolton, Mass., whence the above name was given to it by 

 Mr. Nuttall. Dr. Thomson, several years since, described it under the name of Silicate of 

 magnesia ;* but in his Outlines of Mineralogy, he remarks that it is intimately connected 

 with picrosmine, with which it also sufficiently agrees in chemical composition. Many of 

 the specimens so closely resemble chondrodite, that it is almost impossible to distinguish them 

 by their external characters. They differ, however, in the proportions of silica and magnesia 

 which they contain. 



Composition. Silica 56.64, magnesia 86.52, alumina 6.07, protoxide of iron 2.46 

 {Thomson). 



Geological Situation. Boltonite has heretofore been found only in white limestone. 



LOCALITIES. 



Orange County. Dr. Horton has introduced into his catalogue, three or four localities of 

 boltonite ; and the specimens from some of these have been recognized as identical with 



* Annals <;/ tht Lyceum of Natiual History of Sew- Vork. ill. 50. 



