262 PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 
bite and coccolite; and contained, diffused throughout it, a probably small 
quantity of the latter, as it was unequal in colour. It had a glimmering lustre, 
and a specific gravity of 2° 958. ) 
1°301 grammes yielded— 

Silica, . ‘ 5 S089 
From Alumina, . 5 SOS 
* 604 = 46 + 425 
Alumina, . : : . 21° 864 
Ferrous Oxide, . ‘ . oO OnS 
Manganous Oxide, ‘ . S69 
Magnesia, . : , » 2°92 
Lime, . A ; : . LSe Ss 
Potash, . . 179262 
Soda, . ; : : «L695, 
Water, . 1:°078 
100 * 233 
Insoluble silica, 2° 814. 
I. have lately seen a thin band of the same substance in the imestona 
quarry of Boulchach—S. W. of Abergeldie. 

LATROBITE. 
Most authorities regard Latrobite as being a species distinct from anorthite; 
Dana places them together. This is certainly ill-advised. Anorthite is a lime — 
felspar, with but traces of potash ; Latrobite is a potash lime felspar. bd 
The classification of the felspars is essentially an alcaline one—every consi- 
deration should make it so. Dana unites this with anorthite, from the quan- 
tity of its acid; but it is doubtful if that quantity is the same as in anorthite. 
Latrobite has different angles, and much inferior hardness. ; 
The.specimens I have found were associated with the last mentioned fel- 
spar: There was very little of it; from the appearance and hardness being 
nearly the same, it was taken for rhodonite, until the specific gravity was deter- 
mined. 
The colour was pale rose red, the structure fine granular, the lustre feeble, 
the hardness 5, the specific gravity 2° 749. | 
Two specimens from different parts of the quarry were analysed; the 

