Notice of Topaz and Phenakite. 329 



Such, gentlemen, is a rude outline of the great revolutions of 

 terrestrial vegetation, as the researches made upon this subject, 

 within the last thirty years, have enabled us to trace them. Each 

 day will doubtless add new traits to these details ; but recent 

 discoveries, by confirming the 'results at which we had previ- 

 ously arrived, seem to assure us that this general delineation will 

 not experience great changes when, thanks to the materials that 

 are being collected on all sides for this object, we shall be ena- 

 bled to transform this rough draught into a picture more finished 

 and complete. 



Art. YII. — Notice of a second locality of Topaz in Connecticut, 

 and of the Phenakite in Massachusetts ; by Charles Upham 

 Shepard, M. D., Professor of Chemistry in the Medical College 

 of the State of South Carolina. 



Among specimens which I obtained at the China-stone quarry in 

 Middletown two years since, I find one to be invested with above 

 fifty crystals of Topaz. They measure from ^ to ^ of an inch 

 in length, are very slender, and perfectly transparent, being at- 

 tached by a lateral plane to crystals of albite. Owing to their 

 mirmteness, it is difficult to distinguish, except in one or two in- 

 stances, the leading planes of the forms. In one crystal, I detect 

 the truncation of the obtuse lateral edges, the truncation and 

 bevelment of the acute lateral edges, and the replacement of the 

 acute solid angles by faces inclining to the last mentioned trun- 

 cating planes under angles of about 153°. In addition to which 

 modifications of the primary form, there are also visible the re- 

 placement of the terminal edges by two planes and that of the 

 edges intermediate between these and the angular truncations, by 

 single planes. The future exploration of the quarry will probably 

 lead to the discovery of more perfect crystals of the present spe- 

 cies than have hitherto been found in the United States. 



The Phenakite, it will be recollected, was first recognized as a 

 distinct species by Nordenskiold, in 1833, — the specimens having 

 been derived from the vicinity of Katherinenberg, upon the east- 

 ern slope of the Ural mountains, where it occurs in granitic rock 

 along with emerald and mica. The resemblance of the mineral 

 is said to be very striking to quartz ; like that species, it being de- 



VoL. XXXIY.— No. 2. 42 



