THE MINERALOGY OF SCOTLAND, 443 
4, MACKNIGHT, writing in 1810 of an elevated point of Ben More, says, 
“At this station veins appear filled with quartz, and containing also mica, 
chlorite, and a valuable variety of iron-glance, crystallised in thin tables” 
(Mem. Wernerian Society, vol. i.). 
That which I analysed occurs in large foliated crystals about 300 feet below 
the summit of Ben More, Perthshire, on a small flat, near a knoll on the north- 
east side. It was associated with chlorite, and rarely tourmaline. The colour 
is blue-black ; it has a high lustre. 
This is without doubt Macknicut’s mineral. 
On 1 gramme— 
Titanic Acid, 18°4 
Ferric Oxide, 55° 305 
Ferrous Oxide, 23 * 863 
Lime, 1°344 
Silica, 2 
100: 412 
5. From the hill Crois, north-west of Arrochar, Loch Long, Argyllshire ; 
also from quartz boulders on the shore at head of Loch Long. 
On the hill it occurs in rudely-formed crystals, imbedded in the quartz 
veins of chlorite slate, especially in a quartz cliff about half way up the hill. 
The colour is black, with but a slight tinge of blue. Powder brown. S.G. 4°86, 
On 1 gramme— 
Titanic Acid, . , : : 40:4 
Ferric Oxide, ; ‘ . : 41° 886 
Ferrous Oxide, . ; , 4 ‘ 15-402 
‘Manganous Oxide, .. : ; : 2 
Line, : ; : 1 456 
Silica, .. : wy ee oat | 
100 : 044 
The ilmenites, iserines, and chromites proved so difficult of decomposition, 
that the most extreme perfection of comminution was found to be requisite 
before any of the processes of decomposition availed in resolving with certainty 
the whole quantity operated on. This, as afterwards to be noticed, was not, 
even with that precaution, in all cases accomplished. The following method of 
pulverisation was adopted. If it was found necessary—but not otherwise— 
the chips, cut up by pliers to fragments of the size of small shot, in order to 
separate quartz and other impurities, were crushed, but no more, in a diamond 
mortar. They were then transferred to an agate mortar, which held about 
three ounces of water. About five grains of the crushed mineral were placed in 
the mortar under half an ounce of water, and were rubbed under the water with 
the pestle till the powder was impalpable. About two ounces of water were 
VOL. XXX. PART II. 3 Z 
