PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 13 
1°141 grammes yielded— 
Silica, ; ; : *505 
From Alumina, . ; -022 
“hoF = 46°18 
Alumina, . 5 . A Uke Bs 
Ferric Oxide, 4-] 
Lime, 1°66 
Magnesia, i, OW 
Potash, 8°81 
Soda, dice 
Water, 5:714 
100° 834 
Absorbs ‘2 per cent. of water ; possible impurity unknown. 
Loses its water at the temperature afforded by a Bunsen burner,—talc 
requires a blast furnace for its dehydration. 
Both the stratum of limestone which first shows itself on the coast of the 
Moray Firth, at Sandend, in Banffshire, and which passes up among the flags 
of the Vale of Deskford, Glen Rinnes and Strath Avon, cuts the high ground at 
Inchrory and Loch Bulg, and possibly reaches the low country through Glen 
Tilt,—and that which first appears at Boyne-mouth, coursing to the east of the 
quartzite and causing the ballochs of Glenbucket, Glen Nochty, Strath Earnan, 
and Tornahaish, afford this brilliant margarodite. Throughout it simulates 
talc, and has as its unfailing associate pyrrhotite,—less frequently rutile, and 
sahlite or actynolite. 
MARGARODITE. 
Si. Alp. Fey. Mn. Ca. Mg. Kp. Nap. F. Ho. Total. 
Lambhoga, with Kaolin : . | 50°77 | 81-71 | 1°32 | -28 95 Te ayaa 53 so ee 99°35 
Vanleep, Shetland, with Kyanite, | 45°43 | 29°65 | 8-33 02 Os NWlstie 6:94. || 2:27 ... | 5°29 || 100°42 
Vanleep, Shetland, with Quartz, . | 45°42 | 30°30 | 6°87 82 6 2°6 6:09 | 2°01 | 1:06 | 5:01 || 100°78 
Botriphnie, Banffshire, : = | Apsl ) 29'9) | (7-87 03 "62 72 Net 2D tr. | 5°51 || 100715 
Glenbucket, Aberdeenshire, . . | 46°18 | 31°83 | 4:1 Pe eOOn el Zan Sirois |i tical me Ds fl || 10083 
Black Micas. 
Most geological works enumerate among the constituents of certain granites 
and gneisses,—‘a dark magnesian mica,”—‘‘a brownish-black magnesian 
mica,’—or “‘a greenish-black magnesian mica,’—as the case may be; but 
do not specify what the mica is. 
VOL. XXIX. PART I. D 
