402 Intelligence and Miscellaneous Articles. 



EDWARDSITE, A NEW MINERAL. 



Dr. Shepherd, Prof, of Chemistry, South Carolina, gives the an- 

 nexed account of this substance : 



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 adamantine. Colour hyacinth- red. Streak 

 white. Transparent to translucent. 



Hardness=4-5. Sp. gr.=4'2. ... 4*6 



Chemical description. — Alone before the blowpipe, in very thin 

 fragments, it loses its red colour, becoming pearl grey with a tinge 

 of yellow, and fuses with great difficulty on the edges into a trans- 

 parent glass. With borax, in little fragments, it turns white and 

 gradually dissolves, forming a globule which is bright yellowish 

 green while warm, but colourless 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 blowpipe 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 ap- 

 pearance, 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 incomplete. In 

 some of them, however, the cross cleavage is eminent, in which in- 

 stances the lateral faces exhibit cross striae parallel with this clea- 

 vage, 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- 

 fect crystals, however, are needed than any I have yet seen for de- 

 ducing the incidence of P to the obtuse lateral edge. The diagonal 

 cleavage is almost as perfect as the corresponding cleavage in Silli- 

 manite. So close is the resemblance between the smaller crystals 

 above alluded to and Zircon, that on first inspection I mistook them 

 for that species. 



The Edwardsite occurs disseminated through Bucholzite in gneiss 

 at the falls of the Yantic in Norwich, Connecticut. The Bucholzite 

 is here considerably abundant, forming apparently a small bed, 

 through which are dispersed also individuals of red feldspar, black 

 mica, and more rarely small crystals of blue corundum. The variety 



