384 I0LITHE. PETALITE. PSEUDO-SOMMITE. SIDEROCLEPTE.

augite; and at Vesuvius in fragments of rocks, ejected from that vol-cano.

Species 94. Iolithe. IIaut.

This substance has been found in grains, and in regular hexae-dral prisms, whose lateral edges are sometimes truncated. Its prim-itive form is also a six-sided prism. It scratches glass strongly, andeven quartz feebly. Its fracture is uneven or imperfectly eonchouial,and vitreous ; its spec. grav. is 2.5. It is usually opaque, sometimestranslucent, and its color is violet blue, tinged with black ; its pow- ^der is bluish gray.

If a translucid fragment be so presented to the light, that the visu-al ray is parallel to the axis of the primitive form, its color is a veryintense blue ; but, if the ray be perpendicular to the axis, it appearsbrownish yellow.

Even when in small fragments, it melts with difficulty by the blow-pipe into a pale greenish gray enamel.

It is found near Cape de Gate in Spain in an altered greenstone.Its gangue is a decomposed, argillaceous substance.

Species 95. Petalite. Brong. Broch.

Its color is reddish, and sometimes grayish white. Its fracture isfoliated ; the laminae are interlaced and have a glistening, pearly lus-tre. It scratches glass, but is scratched by feldspar ; and has a spec,grav. of 2.62. It is brittle, and translucent at the edges.—It is infusi-ble by the blowpipe.

It is found at Uton, Sahla, &c. in Sweden .

Species 96. Pseudo-Sommite.* IIaut.

It occurs in very minute, regular hexaedral prisms, sometimes trun-cated on their terminal edges, and also in transparent, shining needles.It is sufficiently hard to scratch glass.

It melts by the blowpipe with some difficulty. Its powder in ni-tric acid forms a copious jelly ; and it is hereby distinguished fromthe Sommite, which it somewhat resembles.

It has been observed at Capo di Bovc, near Rome , in a volcanicproduct with the Melilite.

Species 97. Sideroclepte. Brorg. Broch.

It is yellowish green, translucid, and so soft, that it may be scratch-ed by the finger nail. It occurs in renifonn masses, sometimes group-ed, and having an even fracture with a feeble resinous lustre.

Before the blowpijie it becomes black and shining, but is scarcelyfusible.—It was found by Saussure in Brisgaw.

* Pseudo-Nepheline. Brongxiart.