Penfield and Sperry — Miner cdogical Notes. 321 



tact with glass only during the necessary filtrations. The 

 slight trace, is calculated as Sa 2 0, although it contained traces 

 of lithia, as shown by the spectroscope. 



Crystals from Mt. Antero, Colorado. — In a previous paper* 

 one of us published a description of these crystals from a few 

 specimens which belonged to the Rev. R. T. Cross, of Denver. 

 During the summer of 1887, Mr. W. B. Smith, of Denver, 

 Colorado, secured a large number of crystals, through a min- 

 eral collector, which are now quite largely distributed through 

 mineral cabinets. The difficulty in securing the specimens 

 is their occurrence at an altitude of over 12,000 feet, at a 

 locality which is only accessible during a short period in the 

 summer, after the snow has disappeared. The crystals are 

 attached to quartz, transparent beryl (aquamarine, sometimes 

 with good terminations), and Baveno twins of orthoclase, and 

 are associated with muscovite and octahedral fluorite. All of 

 the specimens which we have seen in the collections of Messrs. 



C. S. Bement, Geo. J. Brush, W. B. Smith, the Yale Univer- 

 sity cabinet and the XL S. National Museum show two prom- 

 inent developments. One of these, according to our own ob- 

 servations and those of Mr. W. B. Smith, who has seen the 

 greatest number and variety of specimens from this locality, 

 always occurs among those crystals which are attached to 

 quartz or beryl and is represented in its simplest form in ^%. 

 2, which shows the combination of a (H2O, i-2) and x (1322, 

 —r\ (f-f)), giving a very interesting form, owing to the un- 

 usual combination of a prism of the second with a rhombo- 

 hedron of the third order ; sometimes there are associated, 

 with these, small faces of m (1010, I), s (21gl, +r J (3-f)) 

 r (10ll,+l), and d (01 1 2, --§-) as represented in figs. 4 and 5 of 

 the previous communication, f The second habit, which is 

 found among those crystals which are attached to orthoclase, 

 has two prisms well developed and is short prismatic, fig. 3, 



* This Journal, III, xxxiii, 132. \ Loc. cit. 



Am. Jour. Scl— Third Series, Vol. XXXVI, No. 215.— Nov., 1888. 

 21 



