504 PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 
1°3 grammes yielded— 
Silica, . : ; °720 
From Alumina, . ‘007 
* 732 = 56 +307 
Alumina, . i ; é TT 
Ferric Oxide, . ; ; 527 
- Ferrous Oxide, . ; . 2Fa2o 
Manganous Oxide, . , °153 
Lime, : ‘ : a 12578 
Magnesia, . ; ; 5 go OUT 
Potash, . : : ‘ *439 
Soda, ; : ; ; “633 
Water, . ; , eile hk) ib 
Insoluble silica, 3-005 per cent. Loss in bath, -32 per cent.; was pure. 
Antigoritic Allomorph—Nephrite. . 
4. I place this very remarkable variety here, on account of its paragenesis 
with the amianthus of Balta. It occurs as a layer, immediately in contact with 
the vein of the former at Doo’s Geo. This layer is about a couple of inches in 
thickness. It presents itself as a fissile schist, which may readily be split up 
into laminze of extreme thinness. Its colour is a very pale pea-green ; it is 
translucent, and altogether so similar in appearance to antigorite that it was 
without hesitation assigned to that mineral. 
Being of extreme toughness, and naturally splitting into axe-shaped frag- 
ments, it would by Dana be classed as nephrite; and in composition it would 
stand immediately central in his list of analyses of that substance. 
It is altogether dissimilar to the amianthus, with which it is associated ; but 
its most remarkable peculiarity is, that where it is exposed to the air it passes 
into it,—the amianthus appearing to grow out of the solid and fissile stone. 
Moreover, although this stone may be scraped down into powder by the 
knife, like steatite or slate-pencil, yet if it be crushed in a mortar or beaten 
with a hammer, it is immediately matted into a felt of amianthoid fibres. 
The lamin of this stone have a rough cleavage in two other directions, 
forming angles of about 122° with each other. This angle is sufficiently near 
the normal to lead to supposition that it may be due to a feeble development 
of crystalline arrangement of parts. Its powder and cut surface are both very 
smooth. Its specific gravity is 2° 957. 

