404 C. 0. Shepard— Mineralogical Notices. 
Pyroclasite—As the series of specimens sent were said to 
have been from caves, which abound at these islands, it would 
appear that their contents fits in percolations across 
Tertiary strata. Indeed, examples ot the lime-rock are 
limestone caves. Portions of the guano-stalagmite are singu- 
larly in the shape of mushrooms; and must have occupied the 
surface of the floor-crust. en broken, their structure is seen 
to be concentrically Jaminated, and not fibrous. In color they 
are brown, intermingled in spots with ash- “Bray, suggestive of a 
composite constitution. Other masses appear to have come 
from the floor stratum itself; and are bard Pa compact, 
with a subconchoidal fracture, like the monetite and like some 
varieties of opal. Its color is brown, though much darker 
and occasionally almost black. It is moreover variegated 
with ash-gray. The specific gravity is 2°62-2°65; hard- 
ness, 35-40. B.B. it decrepitates, emits a seeny organic 
tates, with liberation of much water and strong empyreumatic 
odor. The subjoined analyses give its chemical composition. 
Shepard. Mean results, 
38 
Oo ais ‘0 “ ‘8 0 
CaO (ee 39°98 40°125 
8 ) Eg NGM Pistia been LE WSN said 6°80 6°825 
Phosphate | iron and alumina 2°90 2°900 
Insoluble 0°58 113 O°855 
Water and loss on ignition. ee ere 10°91 10-335 
“98:97 10052 100°120 
Deduet pypane Dee oe te ee 14°670 
ON SOL). Fosse ne eee 0°855 
vs ‘licenhaces iron and alumina 2-900 
“ _ gof loss by ignition, as organic 2°422 
20°847 
79°273 
