PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 459 
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| 6. From Ben Chourn, Glen Elg. 
The sahlite, mentioned as occurring in the lime on the north slopes of Ben 
| Chourn, was found in only a few rounded lumps,. which had. a radiating crystal- 
line structure, the crystals being about two inches in length. The mineral was 
ofa pale leek-green colour, and was coated with an ochrey rust. 
| 1°507 grammes yielded— 
Silica, , ; : . 54:°479 

Ferrous Oxide, . ; ,° Boies 
) Manganous Oxide, . : » 245 
Lime, ‘ ¢ : . 22°86 
| Magnesia, : . 17°584 
Potash, +, ; : : *438 
. Soda, : : : ; “79 
Water, : ; ‘ A * 424 
99-909 
9° 025 per cent. of the silica were insoluble ; possible impurity, unknown. 
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| 7. From the well-known Tiree marble. 
This now almost exhausted marble occurs at Balliphetrich, on the west 
| side of Tiree. It has been admirably described by Maccuttocu in his “‘ Western 
| Islands.” It owes. its peculiarity to numerous imbedded minute crystals of 
| dark green sahlite which are promiscuously sprinkled through a granular cal- 
 careous paste, which is tinged of a peculiar red in blotches. This coloration is 
| due to minute tufts of crystals of a substance afterwards to be noticed. Dr 
| Maccuttocu has remarked upon the rounded and polished outlines of the 
| imbedded crystals of sahlite ; and in SoweErBy’s “ British Minerals,” a peculiar 
pale cross banding (? ¢ cleavages) which they present is admirably depicted. 
_| They are commonly of the size of shot, rarely of large size—an inch or so, 
_ | —sometimes in cleavable masses, and are occasionally associated with a pale- 
| blue, watery variety,* and with minute highly lustrous erystals of sphene, which 
latter also exhibit a rounded contour in their faces. 
Of more marked interest in this marble is the occurrence of portions of 
| Sahlite, in which an incipient as well as a perfected passage into serpentine is 
beautifully: seen. 
At this locality unaltered sahlite, however, prevails :—while, in contra- 
distinction to this, in the Glen Elg limestone there is a very similar sprinkling 
of granules. of yellow serpentine, the unquestionable representatives of former 
crystals of sahlite,—the unaltered sahlite being there the exceptional occurrence. 
* Tn Jamuson’s “ Mineralogical Travels,” vol. ii. p, 33, we see that this pale variety was considered 
corundum by the Hon. Mr Grevitie. Jameson considered the sphenes to be garnets. 
