PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 41 
In many localities the augite and hypersthene both give place to the mica, 
the felspar only remaining the same; these transmutations occur repeatedly. 
At the Barry granite quarry near Knock the mica is hardly to be seen, at the 
Bin of Huntly augite and hypersthene replace it entirely. Where the rock 
appears on the south side of the Burn of Craig, near Towanrieff, the labra- 
dorite has again the mica as its sole associate. A loose block or two of a 
similar rock occurs at New Merdrum near Rhynie ; in these the crystals of both 
minerals are over an inch in size. 
Up the valley of the Blackwater, a bed of diorite, with occasional specks 
of doubtful hypersthene, or in its. place of a black mica, is. to be seen. There 
can be little doubt that it is the same belt of rock which reappears at Glen- 
bucket and Colquhanny, and here hornblende, with a little Haughtonite, is again 
present, menaccanite and sphene also occurring.* 
The lithological position of the new mineral is, therefore, clearly defined and 
altogether distinct from that of Biotite; they never occur together, or replace 
each other in the same rocks. 
Of lepidomelane this cannot, to the full at least, be said. 
Though I have never found it in association with Haughtonite, one of the 
specimens analysed was taken from an exfiltration vein in a rock very similar 
to that which at Lairg carried the Haughtonite ; the other lay bedded in the 
felspathic belt of a hornblendic gneiss. 
It is possible that lepidomelane may also be the dark mica of other gneisses,— 
ex grege, of the peculiarly bronzy gneiss of Tiree, which carries garnet. 
Chemically quite different from the former micas, this is not clearly 
separated from the last in its modes of oceurrence, being found, though only 
once, in an exfiltration vein. Still in Scotland it does not, as in Ireland, per- 
tain to the granites, being here probably solely a gneissic mica. 
Be this as it may, these geologic relations go to establish very clearly the 
specific individuality of Haughtonite. 
Two important distinctive properties remain to be noticed,—crystalline 
form, and chemical features. 
* Localities in which it is doubtful whether the black mica is this species or Biotite are the 
following :— 
At Badnagauch on the Deskery there is a rotting syenite, which is riddled with exfiltration veins 
composed of large crystals of labradorite and hornblende, with a hydrated Biotite (?), menaccanite, 
sphene, and Allanite as accessories, 
In the hyperite of Scuir na Gillean in the Cuchullins, and of Halival in Rum, a black mica is 
rarely seen, which is most probably Biotite. 
Scales of a dark brown uniaxial mica, which occur in tufa at Kinkell and Kincraig in Fife, I also 
set down as Biotite. Haughtonite probably is the brown mica which, in somewhat small quantity, is 
found in the andalusite layers of the gneiss of Clashnaree, Glendarff, and other hills of the Clova 
district. The associates here being andalusite, quartz, fibrolite, and labradorite. The composition of 
the mineral from this locality does not altogether accord with that of the generality of specimens, 
and its occurrence in gneiss is somewhat exceptional. 
VOL. XXIX. PART I. L 
