362 Microlite, a New Mineral Species. 



line. From among them, I selected an exceedingly minute, transpa- 

 rent, yellow crystal, whose faces were sufficiently brilliant to afford 

 me its angles with the reflecting goniometer. It uniformly gave the 

 inchnation of faces united by edges = 109° 30'. 



3. The specific gravity was determined by means of two of the larg- 

 est crystals I could obtain, one of which was that first observed, and 

 the other, smaller, by 0-1 of a grain. The water was at 60° F., and 

 the balances so delicate as to oscillate on the addition of 0*0 1 of a 

 grain. The largest crystal gave the Sp. Gr.=5-00; the smallest 

 =4-75. 



4. Its place in the natural system, if the specific gravity can be 

 relied on, is within the genus Tungstic-Baryte, whose limits of hard- 

 ness are 4*0. ..5*5, and those of specific gravity are 4-5. ..6-1 ; and its 

 specific designation will therefore be. Octahedral Tungstic-Baryte. 



5. The only substance with which the Microlite can be brought 

 into comparison, of which we have any mineralogical account is the 

 Phosphate of Yttria, of Berzelius,* the Xenotime of BEUDANT,f 

 which according to the observations of Haidinger, belongs to the 

 pyramidal system of MoHS, and moreover possesses hardness=4-5... 

 5*0, and Sp. gr. =4-557. It is therefore sufficiently excluded from 

 coalescence with this species. 



6. I have additional pleasure in bringing forward the present min- 

 eral, from the persuasion that every mineralogist has but to examine 

 his specimens from Chesterfield, to find it already in his cabinet. I 

 would apprise such as search for it, however, that the naked eye is 

 not always sufficient for its discovery ; the microscope will generally 

 have to be employed ; and the most likely part of the specimen to 

 meet with it, will be the line of junction between the vein of smoky 

 Quartz, (which contains the Tourmaline,) and the Albite. 



7. My next visit to the locality will, I trust, supply me with 

 specimens sufficient to attempt a more detailed chemical examination 

 of it than is contained in the present notice, and which is barely ad- 

 equate to furnish the conjecture, that its principal ingredient is oxide 

 of cerium. 



* Kongl. Vetenskaps Acad. Handlingar for 1824, p. 334, and Foggendorf s An- 

 Balen der Physik, 1825. II. p- 203. 

 t Traite elementaire de Mineralogie, II. p. 552. 



