a n 

1891.] Mineralogy and Petrography. 829 
Hillebrand” concludes that nitrogen is a constant constituent of the 
mineral, and in a form different from any hitherto observed in the 
mineral kingdom; that its composition varies widely, and with it 
the physical characteristics ; and, finally, that the composition does not 
correspond with any formula proposed to represent? it. The author 
proposes to continue its study, and asks the aid of.mineralogists in 
securing specimens, Excellent transparent crystals of anthophyllite 
have been obtained by Mr. Penfield !8 from Franklin, Macon county, 
N.C. They are prismatic with oP and œP% , but no terminations. 
The ratio a: 4, based in approximate measurements, is .51375: 1. 
The cleavage is perfect parallel to the prism and the brachypinacoid,. 
and poor parallel to the macropinacoid, 2Vna = 88° 46’, with the 
corresponding index of refraction for § = 1.6353; a = ÁA, b = Ð, 
c = C. The double refraction is negative for green and yellow light, 
and positive for red light. Density = 3.093. The composition is: 
SiO, FeO MnO MgO CaO H,O ALO, Loss at 100° 
57:90 16.39 <31- 26.09.20" “2:67 “G9 ‘tf 

— The so-called perowskite ® from Magnet Cove, Ark., proves upon 
analysis to contain niobium and tantalum, and, therefore, to belong 
with dysanalyte, and not with perowskite. Its density is 4.18, and 
composition ; 
CaO MgO FeO Fe,0, (Y.Er.Ta),O, sare Nb,O, TAO, TiO, SiO, 
33-22 .74 .23 6.16 5-42 4.38 5.08 44.12 .08 
—Some new facts with reference to the Jderyls, bertrandites, and 
phenacites from Mt. Antero, Col., are communicated by Penfield.” The 
crystals occur implanted in granite or on the feldspar and quartz of 
this rock. The beryl probably afforded the beryllium for the other 
two minerals. It occurs in light-green or blue prismatic crystals, 
usually simple combinations of P and OP, but occasionally also 
with 2P2 and œP% The peculiarity of the crystals is the number of 
depressions observed on various planes. These are pits bounded by 
pyramidal faces, and into them long needles of beryl project. The 
forms on the needles are 12P8, 12P2 and 2P. The axial ratio of the 
bertrandite is .5993, instead of .5953, as printed in the author’s first 
paper”! on the mineral. Some of the crystals of phenacite are inter- 

17 Tb,, Nov., 1890, p. 384. 
18 Ib., Nov., 1890, p. 394. 
19 Ib., Nov., 1890, p. 403. 
2 Ib., 1890, p. 488. 
21 Ib., XXXVI., 1888, p. 52. 

R EEV E ERE: A 
E E AE AE NS g EEE Peat E A O T kel E a AE Sa N EEA N 


