———— 
PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 529 
If mountain leather be an alteration product, and not an independent 
mineral, amianthus has probably been the original substance. 
Attention may here be directed to the fact that Dr THomson published an 
analysis of mountain leather from Strontian, wherein he gave the quantity of 
water at 21-7 per cent. ; this appeared so excessive that the analysis was not 
admitted ito most works. The above three analyses give much the same 
quantity, and I therefore insert Dr THomson’s analysis along with the above, as 
affording another illustration. The mineral from Tod Head is so impregnated 
with minutely granular quartz that it had to be three times picked and 
analysed before the results accorded with those from the other localities. 
From Amygdaloid. 
23. It has been in accordance with the view generally held,—namely, that 
mountain leather, cork, &c., are products of the alteration of a hornblendic 
mineral,—_that I have inserted them above, but I have lately found in the 
railway cutting in the immediate vicinity of Partan Craig, Fife,* a variety of 
the same, occurring in an association which leaves little doubt of their being, 
sometimes at least, an unaltered and quite distinct substance. 
The highly porphyritic amygdaloid here contains steam cavities filled with 
saponite, agates, and rarely celedonite ; it also has its rents filled with veins, 
about an inch in thickness, of calcite, rarely crystallised. 
The sides of these veins are coated with a fibrous mineral, which also 
rarely is imbedded in the calcite. The fibres are of extreme tenuity, and 
rarely felted; they are highly lustrous, and pure white, rarely passing into 
saponite green, or azure blue. A fitting trivial name would be mountain silk. 
The fibres are tough, and reduced to powder with difficulty. The specific 
gravity is 2° 108. 
1° 201 grammes yielded— 
Silica, . : : - 649 
From Alumina, . - 004 
- 653 = 54: 371 
Alumina, . : : tele 27 
Ferric Oxide, . ; ; “212 
Ferrous Oxide, . : . 1:°094 
Manganous Oxide, . ; 333 
Lime, ; ; : ; “ig 
Magnesia, . : ‘ . 0497 
Water, . F . BP On 

100-158 
* Lately corrupted to Ferry Port on Craig. 
VOL. XXVIII. PART II. 6x 
