Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/516

 rals. As regards the general character of the gangue of the mine, we are struck by the absence of Fluor, and the comparative rarity of Blende and Heavy Spar. The last-named species we might fairly expect to be present in considerable abundance, as baryta is present in such large quantity in the Harmotome and Brewsterite.

During the last six years a new mine r called Corrantee, has been opened, at a distance of some two miles westward from Whitesmith, but at the other side of the hill. It is, however, apparently on the same lode that is worked in Glen Strontian, but is situated entirely in the gneiss. I first visited this mine in 1866, and noticed the presence of the barytic Zeolites. Since that time some very beautiful specimens have been obtained from it, notably of Calcite, in the form of scalenohedrons terminated by rhombohedrons, and coated with Harmotome.

Among other specimens I found some crystals of Harmotome closely resembling those from Andreasberg, in fact true Cross-stone. These were irregularly distributed over a mass of very acute scalenohedrons of Calcite, and associated with minute hexagonal prisms apparently terminated by a basal plane, and perfectly transparent. When I first noticed these crystals I felt sure that I had discovered a new locality for Brewsterite; but on testing the mineral in the blowpipe I found that it did not swell up, and that it gave a simple baryta-flame. The borax-test proved abundantly that it was a Zeolite. These results made me suspect that it was only a new form of Harmotome.

Not being myself able to analyze it y from want of time, I requested my friend Dr. J. E. Reynolds, Keeper of the Minerals in the Royal Dublin Society, to examine it.

He detected that the termination of the prisms is not a single plane, but consists of two planes inclined to each other at a very obtuse angle.

He therefore broke up a large specimen, picked out carefully all the crystals which exhibited this peculiar termination to the prisms, and subjected them to analysis.

He only succeeded in obtaining 1.5 gramme of the mineral by this method, a quantity quite insufficient for a complete analysis, inasmuch as, owing to the necessity of determining the alkalies, he was obliged to decompose the mineral by acid, and therefore could not ascertain the amount of water present.

The following Table gives the best analyses of Strontian Harmotome which have as yet been published ; and it will be seen how closely Dr. Reynolds's analysis agrees with them.

A. B. C. D.

Si O3 47.74 47.52 47.60 48.02

Al2 O3 15.68 16.94 16.39 17.42

Fe2 O3 0.51 0.65

Ba O 21.06 20.25 20.86 20.17

Ca O trace

K O 0.78 1.00 0.81 0.62

Na O 0.80 1.09 0.74

H O 13.19 13.45 14.16 13.77 (water and loss).

99.76 100.25 101.21 100.00