Dr. R. D. Thomson, on the Analyses of Minerals. 87 



XVII. — Analyses of sonxe Minerals, made in Glasgow College Laboratory, 

 by Robert D. Thomson, M. D. 



ZEOLITES. 



Wollastonite. — The name of Wollaston, to whom mineralogy was so 

 much indebted, was given to table spar by Hauy ; but as that beautiful 

 mineral is so universally known by the latter title, the term Wollastonite 

 has become a mere synonym. In the year 1829, a mineral was found at 

 Kilsyth, occurring in veins in a greenstone rock, on the banks of the Forth 

 and Clyde Canal. This species I analysed, when but a very youthful 

 chemist, in the beginning of 1830 ; and as it approximated in composition 

 to table spar, although quite a distinct species, Dr. Thomson gave it 

 the name of Wollastonite, and published an account of it in the Trans- 

 actions of the Royal Society of Edinburgh. A notice of it was also printed 

 in the Records of General Science, Vol. I. p. 220, in 1835. 



The same mineral has recently been obtained in the formation of the 

 Bishopton Tunnel, on the Glasgow and Greenock Railway. About the 

 beginning of this century, an analysis was published by Dr. Kennedy, a 

 very able analytic chemist, of Edinburgh, " of an uncommon species of 

 zeolite," found in the Castle Hill of Edinburgh. (Edin. Trans., Vol. V., 

 and Phil. Mag. XIV., 310.) The analysis agrees so closely with that of 

 Wollastonite, that I have ventured to republish it, and with less hesita- 

 tion, since Lord Cathcart (then Lord Greenock) procured the same mine- 

 ral, some years ago, from the locality in which it was obtained by Dr. 

 Kennedy. Professor Kobell has described, under the name of Pectolite, 

 a mineral from Tyrol, (Kastner*s Archiv. XIII. 385,) which corresponds 

 nearly with Wollastonite ; but the analysis which he has published is so 

 imperfect, that an accurate conclusion cannot be drawn as to its true com- 

 position. 



The description given in Dr. Thomson's mineralogy, Vol. I., 131, I 

 believe to be descriptive also of the Bishopton specimens, with the excep- 

 tion that the hardness is too low. The number given in that volume 

 is obviously a typographical error. The true hardness I find to be, of all 

 the specimens in our private collection, 5*25. 



In the following table, the first column represents the analysis of Dr. 

 Kennedy; the second, my analysis, made in 1830; the third, an analysis 

 of Wollastonite, from Bishopton, made by my pupil, Mr. James C. Steven- 

 son, during the present year ; and the last column represents the compo- 

 sition of the Pectolite of Von Kobell. The specific gravities, as obtained 

 by the different experimenters, are as follows: — 



Kennedy, 2*643 to 2740 



R. D. Thomson, 2*550 2876 



Von Kobell, 2.69 — 



i. n. m. iv. 



Silica, 5150 52-744 52059 5130 



Lime, 3200 31684 32817 3379 



m 



