
PROFESSOR HEDDLE ON THE RHOMBOHEDRAL CARBONATES. 499 
The colour of these pseudomorphs is dull ochre yellow. Their specific 
gravity, taken on perhaps a somewhat porous bit, = 2°742. 
The analysis on 25 grains afforded— ) 
Insoluble, i : gor’ : : : ; 1:780 

Carbonate of lime, . xb : ’ ; : 51:48 
es of magnesia, - : 5 : ; 37°42 
aes ofiron, . : oer nae ; : 7016 
- of manganese, : d : : : 1:928 
99-624 
The four carbonates are here present in the ratios— 
Cad MeG FeC MnG 
51. 42 6 ee 
Its theoretical specific gravity would be 2°93. 
These “ pearl spars ” somewhat approach Ankerite in composition; having, 
however, low gravity, curved faces, and pearly lustre, they are true pearl spars. 
COLOURED CALCITES. 
Pomegranate coloured calcite.—From the old workings at Tomnadashin, 
Loch Tay. Occurs in pale pomegranate red crystals, with cleavage angle 105° 
14’, associated with a ferruginous calcite, sheafy baryte, fahlerz, quate, and 
pyrite. Specific gravity, 2°687. 

Insoluble, . , ‘ ; 4 : 3 ‘004 
Carbonate of lime, . ; : ; 5 . 97°763 
of ofiron, . ; : : : : ‘765 
9 of manganese, : , : , ; 1119 
‘5 of magnesia, : : 4 , : 076 
99°727 
The very peculiar colour was possibly due to a suboxide of copper; derived 
from the adjacent fahlerz ; no copper was, however, actually found. 
Pink calcite occurs in the porphyry south of the town of Gourock, associated 
in druses with white baryte; purple, yellow, green, and colourless fluor; and 
minute needles of a substance much resembling Gothite, but which are 
magnetic. 
Colour of the calcite nearly as bright a pink as that of manganspath. 
Specific gravity, 2°732; cleavage angle, 105° 43’, 
Carbonate of lime, . ; P : 5 : 93:16 
» of magnesia, , F : ; ; “472 
" Ofiron, , ‘ : : ‘ : 1:984 
a3 of manganese, ; 5 : 2 F 4-276 
Alumina, 5 F : : , : ; 044 

99-936 
