Microlite, a Neto DfBneral Species. 361 



Art. XXV. — Microlite, a New Mineral Species ; by Charlks 

 U. Shepard, Lecturer on Natural History in Yale College. 



Primary form. Regular octahedron. 



Secondary forms. 1. The primary with its edges truncated. — 

 2. The primary with its edges truncated, and its angles replaced by 

 four planes resting on the primary planes. 



Cleavage. Imperfect, parallel with the primary faces. In other 

 directions, there is conchoidal fracture passing to uneven. Surface 

 of the primary faces generally dull ; those of the trapezohedron, 

 also; dodecahedral planes too minute for observation. 



Lustre resinous. Color straw-yellow to reddish brown. Trans- 

 parent to translucent. Streak white, except when the color of the 

 mineral is brown ; it then resembles the color. 



Brittle. Hardness = 5'5. Sp. gr.=4-75...5-00. 



Observations. 



1. Alone, before the blow-pipe, it remains unaltered. It is slowly 

 dissolved in glass of borax, to which it communicates a yellow color, 

 which grows paler on cooling, but remains transparent unless subjec- 

 ted to flaming, when it instantly becomes nebulous, and presents on 

 cooling, a.pale yellow enamel. It is not readily acted upon by car- 

 bonate of soda, at least in the mass. 



2. This mineral, named in allusion to the diminutive size of its 

 crystals, from fxix^o? small, attracted my attention many years since ; 

 and a specimen of Albite from Chesterfield, (Mass.) has been pre- 

 served in my cabinet on account of its presenting a portion of the 

 pyramid of this substance, which, however, I had suspected, prin- 

 cipally on account of its color, to be Zircon. Having lately been 

 called to examine it anew, I perceived that the inclination of the 

 faces indicated a regular octahedron, instead of an octahedron with 

 a square base, as its system of crystallization. Tlie crystal was ac- 

 cordingly freed from its gangue, when I instantly recognized it to 

 have the figure of modification 2, in the above description. The 

 size of the crystal was about -^\ of an inch in diameter, and it 

 weighed 0*4 of a grain. I immediately examined other specimens 

 of the Chesterfield rock in my possession, and had no difficulty in 

 discovering a number of crystals, all of which were smaller, dis- 

 seminated through the Albite, and rarely imbedded in the Tourma- 



Vol. XXVn.— No.2. 46 



