264 PHYSIOGRAPHY. 



Hornblende. 



substance, particularly laminae of Pyroxene, interposed be- 

 tween them. Massive: composition granular, .individuals 

 of various sizes, generally strongly cohering, and producing 

 in the large, a tendency to slaty fracture ; composition co- 

 lumnar, individuals of various sizes, sometimes very deli- 

 cate, generally long, parallel, or diverging, and aggregated 

 in a second granular composition. Compositions of short 

 and irregularly distributed columnar particles, possess, in 

 the largo, a slaty fracture. Very thin columnar composi- 

 tion produces -a silky lustre. 



1. Of those varieties of the present species which have obtained dis- 

 tinct names, arid which in some systems of mineralogy, have even been 

 regarded as forming separate species, the following are the most remark- 

 able, viz. Hornblende, Tremolite, Jlctynolite and Jisbestus. The dark 

 blackish and greenish colors constituted Hornblende, which was divided 

 into basaltic, common and slaty ; the first of these affording crystals ea- 

 sily cleavable ; the second such as are of difficult cleavage, and the mas- 

 sive, granular and columnar varieties, excepting such as are jet-black, 

 shining and easily cleavable, which were distinguished under the name 

 of Carinthin, and the third comprehends such massive specimens as ex- 

 hibit a slaty fracture. Tremolite consists of the pale green, grey, bluish 

 and white varieties, and has been divided into common, asbestiform and 

 granular. The first occurs in crystals, rarely with perfect termina- 

 tions, and in massive varieties, in which the individuals are large ; the 

 second in columnar compositions, or coarsely fibrous, with considerable 

 degrees of transparency ; the third refers to very thin or capillary crys- 

 tals; and the fourth consists of granular particles. The varieties of Ac- 

 tynolite differ from those of Tremolite, by their deep green, (often grass- 

 green) colors. The asbestiform tremolite, and asbestiform actynolite, 

 form a passage into asbestus, which term is applied not only to minute 

 columnar, and variously interwoven individuals of this species, but to 

 those also of Pyroxene and some other species, the name denoting 

 rather a peculiar state of aggregation in these species, than the substance 

 of a distinct mineral.* 



* Asbestus in general, has been divided into amianthus, which con- 

 sists of highly delicate fibres, often thinner than a hair, longitudinally 



