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464 PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 
GEIKIE, in the explanatory chapter attached to the Ayrshire Survey, that there 
is no need of enlarging on them. 
The specimens examined were from a low spit, which protrudes far seaward 
about mid-tide level. This consists for the most part of the diallage, in large 
platey and intermatted crystals; these lie imbedded in a granular massive 
hydrated Saussurite ; the rock here, also, being of singularly simple constitution, 
with no accessories. 
The diallage here is an excellent type of this variety of augite: broad 
cleavage foliations, and even crystal faces, flash with a splendent lustre, but with 
a uniformity which is frequently broken by a singular reticulated or arborescent 
appearance ; the interrupting duller structure having the ordinary non-lustrous 
appearance of the stone. 
The pseudo-metallic semi-nacreous flash, brought out in certain positions by 
reflected light, appears to arise from an internal reflection from flat fissures or 
broad cleavages. 
Rough crystals, of half the size of the palm of the hand, may here be obtained. 
The colour is olive-green ; the specific gravity, 3° 251. 
1°3 grammes yielded— 

Silica, : t °66 
From Alumina, . °013 
°673 = 51° 769 
Alumina, . : : sider oa 
Ferrous Oxide, . : ea Oye 
Manganous Oxide, . ; +307 
Lime, < : ; . 22:°098 
Magnesia, . : : . 18°461 
Potash, . ; : : *628 
Soda, F ; 5 : ay gs 
Water : ; : = wk OSS 
99 - 982 
Insoluble silica, 3:863. Impurity unknown. 
Smaragditic Augite. 
12. True smaragdite, according to DEscLoIsEAux, has the-angles and cleay- 
ages of hornblende. Haiprncer found that from Bacher to consist of alternate 
laminze of hornblende and augite, in parallel disposition. 
The mineral which I have designated as above cannot be of such a nature, 
as it has needles of actynolite here and there, in confused arrangement, matted 
into a generally foliated mass, and penetrating the augite crystals. Minute 
transparent gem-like crystals of augite are also to be seen. 
