236 



Scientific Intelligence. 



The crystals are for the most part clustered in open loosely co- 

 herent groups. They are many of them cruciform twins, cross- 

 ing at angles of 102° and 78°, which gives as the twinning plane 



Measured. 



Calculated. 







110 ^ TlO = 120° — 121 



11S° 17' 







110 ^ 111 = 21 c 40' 



22° 17' 





\ m 



106 ~ 106= 40° 32' 



38° 31' 







/-==» — e 







777 





L m "~"T~" 



771 













the unit brachydorne (011, 1-t) for which we have 001 /s 011 = 

 51° 24'. The twins previously described have (101, 1-i) as the 

 twinning plane. The habit of the crystals is shown in the ac- 

 companying figures. 



Pyrite. — A group of crystals from Colorado has yielded an un- 

 usual combination of forms as represented in part in the accom- 

 panying figure. The planes here present 

 are : 



a(100, i-i) 

 l'(\20, -i-2), 



i-2), 

 2-2), 



J(110, I), e(210, 

 o(lll, 1), n(211, 

 m(311, 3-3), "jo(22i, 2), s(321, f), w(851, 

 8-|). The occurrence of both -\- and — 

 pyritohedrons e and I', is unusual ; the 

 measured angles on the cubic plane are 

 26° 36' and 53° 35'. Other edges of 

 the same crystal gave a series of reflec- 

 tions corresponding to the following 

 pyritohedrons, viz: 210, 430, 540, 450, 340, 230, 120. 



15. Barite from Aspen, Colorado; by J. F. Kemp (commu- 

 nicated). — While on a recent visit to Aspen, Colorado, the writer 

 obtained from the Smuggler mines several specimens of beauti- 

 fully crystallized wine-yellow barite, which closely resemble the 

 variety described by Beckenkamp* from the phonolite of the 

 Kaiserstuhl. The ordinary gangue mineral of the Aspen lead- 

 silver mines is common white barite in foliated masses. The 

 Smuggler mine alone seems to afford crystals. The ore body lies 

 in blue Carboniferous limestone and in this particular mine shows 

 considerable zinc. Cavities in the decomposed ore are found 

 lined with the barite crystals. The largest in my possession are 

 about one-quarter of an inch on a side, but others have been 

 found larger. They are tabular in form showing most prominently 

 OP and oo P. Together with these are seen P, ^P<55 , P^o , °°Pgo , 

 P<2 , ooP^, .and a macro-pyramid whose faces, though distinct, are 

 somewhat curved and give measurements which vary several de- 

 grees. mPn^0P=zl0l° — 112°; mPn xs^P^ =153°50' to 156° 40'. 



* Groth's Zeitschrift, xiii, 24, 386. 



