ON A. NEW MINERAL FROM INVERNE8SHIRE. 109 



9. On an apparently New Mineral occw^ring in the Eocks of 

 Invernesshire. By William Jolly, Esq., F.R.S.E., H.M. In- 

 spector of Schools, Inverness, and J. Macdonald Cameron, Esq., 

 Fellow Inst. Chem., F.C.S., of the Chemical Laboratories, South 

 Kensington Museum. (Eead June 11, 1879.) 



(Communicated by Prof. J. W. Judd, F.E.S., Sec. G.S.) 



[Abstract.] 



I. Its Geological and Geographical Distribution. 



The Moray Firth, from Duncansbay Head to Buckie, is enclosed 

 by the Old Eed Sandstone, except some Jurassic patches near Brora 

 and Cromarty, and others near Elgin. In this area it is touched by 

 no Silurian except for a few miles between Inverness and Beauly. 

 The Old Eed Conglomerate and other beds exist west of Inverness 

 in a triangular patch between Dochgarroch and Bunchrew. The 

 Silurian to the west of this forms an oblong semidetached area 

 surrounded by Old Eed, except for a few miles on the south. 

 This Silurian patch has a general slope to the Moray Firth on the 

 north, into which it is drained. Its main stream is the Moniack 

 Bum, rising three miles north of Drumnadrochit in Glenurquhart, 

 running generally along its centre and falling into the sea west of 

 Lentran. The strata form a syncline, the axis striking roughly 

 N". and S., the rocks on the east dipping to N.W., those on the west 

 dipping generally to S.E., but the latter much disturbed. They con- 

 sist chiefly of clay-slate, micaceous and chloritic schist, and gneiss. 



A limestone, worked at several points, runs parallel to and near the 

 axis, of varying thickness, sometimes twelve feet, and often concre- 

 tionary and interbedded with other rocks. A red granite also 

 occurs in the Silurian near Abriachan ; it is of commercial value, 

 and known as Loch-lN'ess granite. 



Within this Silurian area the mineral which was the subject of 

 the paper occurs at five points, at three of these in situ, and has as yet 

 been found nowhere else. It is of a blue colour of various shades, 

 from ultramarine to bluish white, often striking and beautiful. It 

 occurs generally in a felspathic matrix, readily disintegrates under 

 water to a fine, blue, soapy, unctuous clay (caused probably by the 

 magnesia it contains), and is seldom found pure, and never yet in a 

 crystalline form, though it sometimes presents a glistening crystal- 

 line aspect. The sites where it has been found are these ; — 



(]) Englishton Moor. — On the west side of Bunchrew Burn, a 

 little above the Public School of Kirkton, at No. 23 croft, near an out- 

 crop of limestone. It occurs here only in scattered blocks evidently 

 carried from the west at Moniack Burn, where it is in situ. It is 

 chiefly found in thin veins and plates in felspar. It was here that 

 the mineral first attracted special attention, during an excursion of 

 the Scientific Society and Field Club of Inverness, on September 1st, 



