Prof. How on the Mineralogy of Nova Scotia. 35 



Of the various modes in which the constituents of the mineral 

 may be arranged, I prefer the following, and therefore, using 

 the notation employed in mineralogy, propose the formula 



2CaO Si0 2 + 2(CaO 2B0 3 , HO)+B0 3 , 3HO 



as that of the new mineral to which I give the name silicoboro- 

 calcite, chosen as companion to that of natroborocalcite, the es- 

 sential chemical difference between minerals found in the same 

 region, and even, as will presently appear, in the same matrix, 

 occasionally being clearly indicated by these appellations : the 

 formula of the latter, according to my own results, when re- 

 written so as to include some grouping seen above, is 



Na0 2B0 3 , 10HO + 2(CaOBO 3 , HO) + BO 3 , 3 HO. 



For comparison's sake, I add the formula of cryptomorphite 

 (the other borate found in gypsum here), also rewritten, 



NaO 2B0 3 , 6HO + 3(CaO 2B0 3 , HO) +B0 3 , 3 HO, 



so that relations can be traced between these geologically allied 

 minerals. 



The constituents of silicoborocalcite are those of datholite, 

 the only other known hydrated silicated borate of calcium, for 

 which Berzelius gave the formula 



CaOB0 3 + Ca02Si0 2 +HO, 



an expression exhibiting proportions very unlike those shown 

 above to exist in the new mineral. In datholite, as in all sili- 

 cated borates, the boracic acid is sometimes held to be basic *. 

 On this view, excluding water, 



In datholite the ratio of in SiO 2 to that in the bases is 4 : 5 

 In silicoborocalcite „ „ „ 4:19 



The ratio of the same to that in all the constituents is in the 

 former 2:3, in the latter 2:12; the relations thus brought out 

 in silicoborocalcite are so unlike those in any known compound, 

 that silica cannot be the only acid present. The formula I have 

 proposed contains two of Wollastonite, two of normal hydrated 

 biborate of calcium, and one of Sassolin. While datholite and 

 silicoborocalcite are quantitatively unlike and physically different 

 on comparing the ordinary crystallized specimens of the former 

 with the nodules of the latter above described, there is a remark- 

 able resemblance between these and the exceptional state in 

 which Whitney found datholite in a greenish magnesian silicate 

 near Lake Superior. I refer to the perfectly white and opake no- 

 dules looking like the finest marble, or some kinds of Wedgewood 



* Dana's ' Mineralogy,' 4th edit., vol. i. p. 207, and vol. ii. p. 335. 



D2 



