162 Description of Edwardsite. 
Art. XVI.—Description of Edwardsite, a New Mineral; by 
Cuarces Uruam Sueparp, M. D., Prof. of Chem. in the Medi- 
cal College of the State of South Carolina. 
Mineralogical description.—Primary form. Oblique rhombic 
prism. M on M=95° (common goniometer.) Base oblique from 
an obtuse edge. 
Secondary form. The primary, with the acute lateral edges re- 
placed by single planes inclining to the adjacent lateral faces under 
137° 30’ common goniometer.) In very minute crystals, the sum- 
mits are occasionally surmounted by four-sided pyramids whose faces 
correspond to the lateral edges of the prism. 
Cleavage parallel to the bases sometimes distinct, but more com- 
monly uneven: in the direction of the longer diagonal very perfect. 
Surface generally not very smooth, but nearly of the same quality 
on the different faces. 
Lustre vitreous to aiitien Color hyacinth-red. Streak white. 
seonscarent to translucent. ; 
rdness=4,.5. Sp. gr.=4.2 ... 4.6. 
Chemical description.—Alone before the Bowne, in very thin 
fragments, it loses its red color, becoming pearl grey with a tinge of 
yellow, and fuses with great difficulty on the edges into a transparent 
glass. With borax, in little fragments, it turns white and gradually 
dissolves, forming a globule which is bright yellowish green while 
warm, but colorless when cold. When powdered, it is acted upon 
very slightly, by aqua regia. A small quantity placed on platinum 
foil and moistened with sulphuric acid, tinged the flame of the blow- 
pipe green. 
General observations.—The crystals are rarely above one third 
of an inch in length by one sixth in breadth. The replacement 
of the acute lateral edges is deep, imparting to the prism a flattened 
appearance, except in the case of very minute crystals surmounted 
by pyramids ; these scarcely exhibit any alteration of the primary 
prism. The terminations of the larger crystals are always incom- 
plete. In some of them, however, the cross cleavage is eminent, in 
which instances the lateral faces exhibit cross strie parallel with this 
cleavage, analogous to certain varieties of Hornblende and Pyroxene. 
The nearest approximations to the value of the angle of inclination 
between the base and the prism was 100° for P on M. More per- 
