PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 525 
than the spot whence the altered augite was taken, specimens very similar in 
appearance to bronzite were found lying loose ; these were traced to a bed of 
what appeared to be an unaltered or little altered hornblende. This was devoid 
of any bronzy lustre, which was now seen to be clearly the result of alteration. 
The mineral was in broad cleavable masses, of a dark green colour, a structure 
between foliated and fibrous, a slightly greasy lustre, and a hardness a little 
Jess than the normal. The specific gravity was 3°01. 
1-302 grammes yielded— 

Silica, . : ? °661 
From Alumina, . pier 
663 = HOO A: 
Alumina, . 1°893 
Ferric Oxide, 9+427 
Ferrous Oxide, . ; = 82085 
Manganous Oxide, . ; 307 
Lime, , ; ; . 8°645 
Magnesia, . . : . 21°582 
Potash, . ; i : 343 
Soda, : : : E *433 
Water, : : : = 4:°536 
100° 172 
Loses in bath - 454 per cent. of moisture. 
Comparing this with the analysis of the altered augite which was found 
about a hundred yards from this locality, the greater durability of the horn- 
blendic type of mineral is well shown; so slight, indeed, was the apparent 
change, that the eye alone could not have detected it, nor could so extensive an 
amount of peroxidation of the iron have been supposed compatible with the 
retention of a bright green colour and a brilliant lustre. 
This is the only hornblende which I have met with in which the broad 
foliated massive variety showed any such change. It may be theorising over- 
much to suggest that the state of change in the more readily decomposable 
surrounding mineral had induced a similar state in this. Doubtless the 
bronzy-looking specimens had suffered a still greater amount of change; the 
bronzy tint being merely superficial, they were not analysed. 
* The occurrence of this variety is another proof of the undesirableness of naming minerals from a 
Single external character. There are numerous bronzy minerals in Scotland ; I do not know that true 
bronzite occurs. The name is nearly as unsatisfactory as is that of chlorite. 
VOL. XXVIII. PART II. 6 U 
