“Account of some new Vesuvian Minerals. 263 
Dimensions. The large crystals are 30 millimetres in 
length, 22 in breadth, and the same in thickness. Still it is 
dificult to measure them, as they are mostly broken at the 
angles, imbedded in the matrix, or covered with pumice. 
lours. Brown, yellow and reddish. It occurs trans- 
parent, translucent, and opaque. 
Position. It is found in small geodes of granitoid aggre- 
gates, composed principally of pyroxene and mica 
these aggregates have their interior full, or studded with erys- 
tals of other substances, passing into enamel, pumice, scoriz, 
or obsidian. Among these volcanic substances are found 
crystals of Christianite, sometimes perfect, or split, or broken 
—semi-fused externally, or covered with a coating of pumice 
or enamel. The aggregates of this nature are mostly uni- 
form or globular, and are found in the matters ejected at 
different eruptions—especially in beds of volcanic sand or- 
ashes. 
The crystals most frequently accompanying this mineral, 
are pyroxene and mica—more rarely hornblende, haiiyne, ido- 
crase, and meionite. ese are found in the same geode 
intimately grouped with it—penetrating its crystals, or being, 
penetrated 
y them. 
This mineral is found in the current of lava at Pollena, 
especially the hexahedral variety, which is accompanied by 
phosphate of lime, melilite, mica and quartz. 
Distinguishing Characters. Its form being derived from 
the the oblique rectangular prism, distinguishes it from 
phosphate of lime, the form of which is derived from the regu- 
lar hexahedral. It dissolves partially, the phosphate entirely 
in nitric acid. Sp. gr. is 2.77—2.92 ; that of the phosphate 
is 3.0—3.2. 
he topaz, peridot and chondrodite are infusible, like 
the Christianite, but the topaz scratches quartz, which in its 
turn scratches Christianite. The sp. gr. of topaz, is 3.56. 
—that of Christianite 2.9. The form of peridot is a straight 
rectangular prism; that of Christianite an oblique rectangular 
prism. The sp. gr. of peridot is 3.4. hon e has 
the oblique rectangular prism for its primitive form, as has the 
Christianite » but in this the lateral face is to the base as 94° 
to 86°—the chondrodite is 112° 12’ and 67° 48’. Nitric 
acid has no power on chondrodite, but dissolves a portion of 
Christianite. The colour of Christianite is rarely yellow— 
