224 



PHYSIOGRAPHY. 



Garnet. 



above, among the crystalline varieties, also grains and massive speci- 

 mens: it contains likewise every shade of the series of colors, and it is 

 therefore only in the particular union of several of these properties, that 

 we must look for the distinction of the above mentioned varieties. The 

 color of Precious Garnet is always red ; its crystals are found imbed- 

 ded. It is the only variety that occurs in grains, and if compound, it 

 presents lamellar composition. Common Garnet seldom occurs in red 

 colors, and these are of dull shades ; its crystals are generally implant- 

 ed, and the composition is granular, but not impalpable. Colophoniteis a 

 compound variety of yellowish-brown and reddish- brown, or oil green 

 and honey-yellow colors, consisting of roundish particles of composition, 

 which are easily separable. If the composition be impalpable, Allochro- 

 ite is formed. The two varieties Jlplome and Essonite, appear less con- 

 nected with the rest of the species, than any of those which have been 

 enumerated. The first of these occurs in dodecahedrons, having the 

 acute, solid angle replaced by tangent planes, parallel with which cleav- 

 age takes place, thus indicating the cube as the system of crystalliza- 

 tion to which they belong. The latter, according to HATJY, presents 

 traces of cleavage parallel to a prism of 101 40'. It is generally found 

 in grains ; but the optical examinations of Dr. BREWSTER and M. BIOT, 

 render it extremely probable that it is only a variety of Garnet. 



2. Before the blow-pipe, Garnet melts without effervescence, pretty 

 uniformly, into a black globule, presenting a vitreous lustre. Some 

 varieties present a slight effervescence, but finally yield the same result. 

 The bead obtained by melting is frequently attracted by the magnet. 



3. Analysis. 



KLAPROTH. 



SIMON. VAITQUELIN. KL. LAUGIER. KL. 



Besides these, Colophonite contains 6-5 p. c. of magnesia, 0-5 p. c. of 

 oxide of titanium, and TO of water; Allochroite, 60 of carbonate of 

 lime ; Pyreneite, 4-0 of water ; and Pyrope, 10 of magnesia, and 2-0 of 

 chromic acid. 



4. Garnet occurs in many rocks with a degree of constancy, and in a 

 quantity almost sufficient to be regarded as an essential ingredient in 



