Blue Feldspar Enlarge
Exotic Mineralogy
Argilla ambigua

Blue Feldspar

  • Syn.
    • Feldspar bleu céleste. De Born. I. 378.
    • Dichter felds-spath. Emmerling, I. 271.
    • Splittriger Lazulit. Karsten, tabl. 46.
    • Feld-spath bleu? Haüy, II. 605. tabl. 60.
    • Feldspath compacte bleu. Bourn. Catal. 58.
    • Blue Feldspar of Krieglach. Aikin, 188.
    • Blauspath. Werner.

This long known mineral has been so generally treated of as a variety of compact Feldspar, that modern writers seem to hesitate in considering it as a distinct species from it; but the result of its analysis should clear away all doubts on that head, even though the laminæ be found to correspond with Feldspar in their direction, being perpendicular to each other. Its relation to Azurite is closer, both in general appearance and composition, but it is softer and heavier: the Azurite is also more distinctly laminated, and the laminæ appear to be slightly inclined. Since; Azurite itself, from the obscurity of its characters, is not a well established species, it is difficult to say how far Blue Feldspar may be connected with it; I therefore still consider it as an ambiguous mineral, and have named it accordingly, in the hopes that something may be hereafter discovered that will throw a light upon both species, and wipe away an unscientific appellation. Blue Feldspar is disseminated among massy Quartz, accompanied with Talc in the fissures, in the same way as common Feldspar occurs in Granite; it has only been found in the valley of Murz, near Krieglach, in Stiria where it is abundant. I am indebted to Professor Cheirici for specimens brought by himself from that spot.

The specific gravity is from 3.046 to 3.060: before the blow-pipe it loses its colour, but does not melt alone: aided by Borax, it affords a black glass.

Klaproth’s analysis gives the following proportions:

Argilla 71.00
Silicia 14.00
Magnesia 5.00
Lime 3.00
Potash 0.25
Oxide of Iron 0.75
Water 5.00
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