
260 PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 
ANORTHITE. 
From Anorthie Diorite. 
1. The rocks at the south-east corner of the bay of Trista in Fetlar, in Shet- 
land, exhibit a good section. 
A graphitic slate is succeeded on the east by an ordinary clay state, that 
by diorite, and that in turn by serpentine. 
The association of mineral constituents in the diorite being unusual, the 
propriety of the name assigned to it may be questioned. 
It is best seen in a gentle height about due east of the bay. Its appearance — 
is quite startling ; the diorite of Glenbucket may be more striking when con- 
sidered in detail, from the great size of its crystals of hornblende; but regarded — 
as a rock mass, I know of nothing so striking as this in all Scotland. i 
‘When broken into, it is found to consist of an almost compact crypto-— 
crystalline cream-coloured felspar, containing imbedded crystals of dark green, — 
somewhat dull hornblende, several inches in size. In the slightly weathered — 
surface the felspar is quite white, while the hornblende is jet black and highly — 
lustrous. . When seen in sunshine, with the light flashing from the crystals of — 
hornblende, the effect is so extraordinary, and the appears altogether SO 
so ina an object. 
The felspar, which proved to be anorthite, was both hard and tough ; i g? 
specific gravity was 3° 099. = 
1-511 grammes gave—— 
Silene Wh baeekaeye 
From Alumina, Sie, es) " 
. -'709 — | 46:922 
Alumina, t 3 a0 dd 
Manganous Oxide, . exo bT, 
Magnesia, ideas . +094 
Lime, , aS . 16°344 
Potash, : ‘ : » 1498 
Soda, ‘ s ; . 3°066 
Water, 4 : : A a5 85 

100°237 
Insoluble silica, 10: 24 per cent. ; there was absolutely not a trace of 1 iron, so 
that there could have been no contamination from hornblende, the only 

