———— 
PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 481 
Allomorphs of Augite. 
Vitrified Augite—--Augitic Glass. 
From Volcanic Rocks in the Coal Formation. 
19. So far as I know, this peculiar variety of the mineral has not before 
been described. 
I first obtained it in a small dyke in the tufa, a little to the west of the old 
summer-house on Elie-ness. It occurred totally filling small druses, or else in 
rounded lumps of the size of pigeon’s eggs ; these lumps were fissured in every 
direction to such an extent that the mineral fell to pieces on attempting to 
extract it. The fragments showed conchoidal fractures on all their sides: a 
high vitreous lustre, a deep greenish-brown colour, and they were slightly 
translucent on the edges. They were set down without hesitation as a highly 
-ferruginous and somewhat dull-lustred olivine. No cleavage could be 
obtained; the fragments, on the smallest application of force, falling into 
minute portions, with a facility which seemed to point to unequal tension in 
the particles—as in the case of the Prince Rupert’s drop. 
The only associated mineral was pyrope in imbedded fragments. 
Similar specimens were also obtained from an intrusive dyke, which 
cuts tufa about half a mile to the east of the above-mentioned locality. 
There were here no closely adjacent minerals, the nearest being Delessite, 
sanidine, glauconite (?), cleavable and brilliant black hornblende, and 
nigrine. 
The mineral was very dense, reaching the high gravity of 3 - 327. 
1-303 grammes yielded— 
Silica, ‘ : °625 
From Alumina, . °014 
* 639 = 49-04 
Alumina, 9°71 
Ferric Oxide, 126) 
Ferrous Oxide, . BY L5G 
Manganous Oxide, . , * 306 
Lime, t i f Y 16254 
Magnesia, : : . 16°884 
Potash, . ; : ‘ “Old 
Soda, : . : : ie 
Water, . ; ; : *305 
100 * 008 
VOL. XXVIII, PART IL 6 1 
