394 Miscellanies. 
17. Scueerer on Aventurine Feldspar.—Aventurine feldspar has been 
found by Scheerer to owe its iridescence to minute crystals of specular 
iron or titanic iron, instead of mica as generally stated. Scheerer con- 
cludes from his various microscopic investigations of minerals, that the 
microscope should be used before attempting an analysis, especially with 
cleavable minerals which are especially liable to mechanical mixtures, 
(Poggendorf’s Annalen, Ixiv.)—Jameson’s Jour., July, 1845, p. 195. 
18. Spadaite, a new mineral; by von Kopett.—This species is near 
Schiller-spar in composition. Color reddish or flesh-red, streak white, 
lustre glistening or glimmering, hardness 2°5, compact with an imperfectly 
conchoidal fracture; soluble in muriatic acid with a residuum of gelatin- 
ous silica. Its formula is 4MS*-+-M Aq*. (Berz. Jabresl. 24th. Jahrg. 
281.)—Jameson’s Jour., July, 1845, p. 194. 
19. Descriptions of Polycrase and Malacrone, two new minerals; by 
Scneerer.—T hese minerals are generally associated with orthite, and are 
often accompanied with phosphate of yttria at Hitterde, Sweden. The 
polycrase is near polymignite. It is without cleavage and has a con- 
choidal fracture, breaking easily. Sp. gr. 5°105, color pure black; thin 
splinters translucent and yellowish brown, streak grayish brown, lustre in- 
ferior to that of polymignite. A qualitative analysis afforded titanic acid, 
columbic acid, zirconia, yttria, oxyds of iron, uranium, cerium, with traces 
of alumina, lime, and magnesia, Malacone, is so called from its having in- 
ferior hardness to zircon. Its form is similar but not identical; cleavage 
none, fracture conchoidal, hardness 6, sp. gr. 3°903, color bluish-white, 
though often brownish, reddish or yellowish from a coating of foreign sub- 
stances, Lustre vitreous, but resinous on a surface of fracture. Trans- 
lucent in small fragments and of a yellowish-white color. Streak color- 
less. Composition, silica 31°31, zirconia 63°40, oxyd of iron 0°41, yttria 
0°34, lime 0°39, magnesia 0°11, water 3°03=98:99. It appears to be a 
zircon containing water. Scheerer considers it probable that the zirco- 
nia exists in malacone in a different isomeric condition from the zirconia 
in zircons. (Keilhau’s Gaea Norwegica.)—Jameson’s Jour., July, 1845, 
p. 192. ; ’ 
20. R. Paurs, IJr., on the State of Iron in. Soils.—Mr. Phillips 
shows. by his analyses that in most rich soils the iron is found principally 
in the lower state of oxydation, and urges that the presence of this oxyd 
is not injurious to vegetation. He explains thus the fact that this oxyd 
remains unchanged ; the peroxyd, he states, is converted to protoxyd by 
means of the affinity of the carbon of the organic matter or humus 
thet This he appears to confirm by experiments. He adds as fol- 
ows :— 
