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POPULAR SCIENCE REVIEW. 
felspar, scattered in every direction. Basalts, which to the naked eye 
appear perfectly structureless, are seen with the aid of the microscope to 
present a series of different constituent particles ; and from an examina- 
tion of this kind several interesting particulars relative to the decom- 
position of these rocks may he gleaned. Even pitch-stones have been 
shown to consist of clusters of beautiful needle-shaped crystals. — ( Pro- 
ceedings of the Imperial Academy of Vienna, 1863.) 
Amblygonite. — This mineral, which until recently had been found only 
in Saxony, has been minutely described by M. des Cloizeaux. His 
specimens were some of them obtained from the State of Maine, U.S., 
and had been presented to him by the distinguished mineralogist, Professor 
Brush. “It possesses three unequally easy cleavages, which are parallel 
to the faces of the primitive parallelipiped, and form angles of 135°, 105°, 
and 88° 30'.” 
Reproduction of Rutile, Sagenite , Brookite , and ArTcansite. — The artificial 
formation of minerals is a subject of much interest, and one also to which 
considerable attention is given nowadays. M. de Hautefeuille has been 
engaged in experiments with a view to produce the above compounds in 
their characteristic natural crystalline forms, and has succeeded almost 
beyond expectation. Rutile may be easily obtained by passing a stream 
of hydrochloric acid gas over a mixture of chloride of potassium and 
titanate of potass. The mixture, contained in a platinum capsule, is placed 
in a large earthen crucible, and is heated to redness, and the acid gas is 
allowed to play upon the mixture by means of porcelain tubes luted to the 
cover of the crucible. The titanic acid, set free and modified by the 
hydrochloric acid, crystallizes in clustered and connected prisms. These 
crystals are yellow and transparent, and present the same angular 
characters as those prepared by M. St. Claire-Deville from amorphous 
titanic acid. Their specific gravity is 4*3, a circumstance which shows 
their identity with rutile. 
Sagenite. — If a current of hydrochloric acid gas be passed over a mix- 
ture of titanic acid, silicium and fluosilicate of potash heated to a bright 
redness, an immense number of minute needle-shaped crystals are formed. 
These crystals are of a yellowish grey, present angles of 90°, and have 
the same chemical composition as rutile. In fact, they are quite analo- 
gous with Saussure’s sagenite. 
Brookite. — If the above mixture be exposed, at a dull red heat, to a 
current of hydrochloric acid, the crystals then produced present trans- 
parent plates of a very fragile nature. Silica is not found in these 
crystals, but their density and form are exactly the same as those of the 
lamellae of brookite obtained from the rocks of Saint-Gothard. 
Arkansite. — If the foregoing operation be carried on in a vessel with 
animal charcoal, black crystals with triangular faces and a deeply striated 
rectangular face, are produced. These crystals have been shown to have 
exactly the same density as those of arkansite ; hence the conclusion that 
they are that mineral, produced by artificial means. 
The Nature of Jade. — Dr. Sterry Hunt, in commenting on the memoir 
of M. Damour, observes that the examination of this mineral and its 
allies furnishes us with the materials necessary for the framing of a law 
