Sommite, Nepheline Enlarge
June 1 1811 published by Jas Sowerby London.
Exotic Mineralogy
VIII
Argilla nebulosa

Sommite, Nepheline

  • Syn.
    • Sommite. Lamentherie Théorie de la Terre, 2nd edit. 2. 271. Sowerby’s Catalogue. pt. 1. p. 24.
    • Népheline. Haüy, 3. 186.

Found as yet only at Mount Somma, close by Vesuvius in Italy, seldom in any larger crystals than the present specimen, which is in the possession of Count Bournon, by whose friendly favour it is here figured. The crystals (see the right hand figure) are short or flattish six-sided prisms; a few are truncated on the lateral edges; see the left hand figure. Mostly shining with a glassy lustre. Fracture parallel with the sides of the prism. Cross-fracture conchoidal. It is inclined to a grey milky white, not very transparent. It scratches glass easily. The matrix is yellowish and dark brownish idocrase, hornblende and some mica.

By the action of nitric acid it becomes opaque and and cloudy, but does not dissolve. It melts , with the help of the blowpipe, difficultly into a compact glass. Spec. Grav. 3.2741.

Analysis by Vauquelin.
Silica 46
Alumine 49
Lime 2
Oxide of Iron 1
Loss 2
100
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