ORDER VI. PJIISMATIC FELD-SPAK. 251 



Lime 2-00 20-80. 



Oxide of Iron 1-00 MO. 



Oxide of Manganese 0-00 12-60. 



Potash 0.00 12-00. 



Before the blowpipe upon charcoal its edges are rounded 

 off. It yields a colourless vesicular glass, but cannot be 

 melted into a perfect globule. Fragments of it thrown 

 into nitric acid lose their transparency, and assume a nebu- 

 lous appearance. This has suggested to HAUY the name 

 of Nephdine. 



2. Rhoinbohedral Feld-spar chiefly occurs at Monte 

 Somma, in the cavities of limestone rocks ejected by Vesu- 

 vius, along with pyramidal Feld-spar and Garnet, with 

 rhombohedral Talc-mica, &c. It has also been found in 

 narrow veins, traversing a kind of basalt or lava at Capo 

 di Bove near Rome, sometimes associated with paratomous 

 Augite-spar. 



2. PRISMATIC FELD-SPAR. 



Prismatic Feld-spar. JAM. Syst. Vol. II. p. 1. Man. p. 

 154. Felspar. Ice-spar. Cleavelandite. PniLL.p. 113. 

 206. 377. Feldspath (Gemeiner Feldspath, Adular, La- 

 brador, Glasiger Feldspath). Eisspath. WERX. Hoffm. 

 H. B. II. 1. S. 295. 369. Feldstein. HAUSM. II. S. 

 528. Feldspath. LEONH. S. 468. Feldspath. HAUY. 

 Traite', T. II. p. 570. TabL comp. p. 35. Traite' 2de 

 Ed. T. III. p. 79. 



WEISS. Schv/eigger's Journal. X. 223. ID. Abhandl. der 

 Acad. der AVissensch. in Berlin fur 1816 und 1817. 

 FUCHS. Denkschr. der Adad. der Wissensch. zu Miin- 

 chen, fur 1318 und 1819. G. ROSE, iiber den Feld- 

 spath, Albit, Labrador und Anorthit. Gilberts Ann. 

 der Phys. 1823. St. 2. 



Fundamental form. Scalene four-sided pyramid. 

 P = 134 57', 126 12', 72 43'. Inclination of 

 the axis, in the plane of the long diagonal 

 0'. Vol. I. Fig. 41. R. Q. 



