PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 43 
acids, it is found that the former acid decomposes all; leaving scales of glistening 
silica in times which bear for the three, as arranged B.L.H., about the propor- 
tions of 1,2, and 4. Sulphuric acid splits up the larger flakes into fungoid 
masses, accomplishing the same decomposition in times about 3, 5, and 9. 
When gently heated, however, the action of the sulphuric acid overtakes the 
more immediate action of the hydrochloric, the thorough decomposition being 
accomplished by the former in a considerably shorter time. 
As might be expected from the large quantity of ferrous oxide in its com- 
position, Haughtonite is subject to change on exposure. 
At the one locality of Nishibost, the edges of the foliz are covered with a 
bright red rust ; elsewhere there is the development of first a dark green, and 
ultimately of a light green colour; the folic at the same time becoming friable 
and talcose ;—the incipient change is well seen at Lairg, in Sutherland, the 
completed one at Blirydrine, Kincardineshire. 
When it occurs as the cryptocrystalline constituent of granites and 
granitites, there can be little doubt that the peroxidation of the mineral is a 
chief cause of the rotting and disintegration of these rocks. 
Granites, with feeble cohesion of their parts to a considerable depth, and 
which crumble rapidly into fine gravels, are to be seen at the south-east foot of 
Morven, and along Culbleen in Aberdeenshire. At Strontian in Argyle, whole 
banks of such gravel have to be dug through before anything like rock is 
reached. The springs of these districts are highly chalybeate: the changed 
mica has become bronzy or ochre-coloured, and talcose to the sense of touch. 
Peroxidation is in such cases the agent of waste. 
One other question remains to be considered: seeing that the marked 
distinction between Haughtonite and lepidomelane lies in the state of oxidation 
of the iron, may the latter mica not be merely weathered or peroxidised 
Haughtonite ? 
As regards the Achadhaphriz and Ben Bhreck specimen, the answer is a 
distinct negative ; from both localities the specimens were perfectly unaltered. 
The Achadhaphriz block had been broken up but a few days before the plates 
were removed from it ; the Tongue boulder was split up by dynamite immedi- 
ately before the collecting of what was analysed; and the associated minerals 
were all unchanged. 
Altered (?) Black Mica. 
From Eajiltration Veins in Syentte. 
The exact nature of the specimens now to be described it is not easy to 
assign, as they may have undergone more or less change. 
They occur in the rocky bank of a road-cutting, which had been made only 
