

126 Fourth Supplement to Danas Mineralogy, 



•w 



Dr. Genth's analyses for the Hitchcockite differ from these in affording a proportion 

 of 2 : 5 bet'sveen the oxygen of the lead and phosphoric acid, and of 2 : 3 between 

 that of the alumina and water, which would be a difference of importance if fur- 

 ther analyses should prove that the composition is constant, which is hardly to be 

 expected. — d,] 



Pyrargteite AyD Proustite [p. ^7, 78]. — From a paper by Q. Sella (Acad, Sci. To- 

 rino, 1856), we cite the following crystalline planes of Red Silver, not mentioned in 



the Mineralogy. — Rhombohedrons -^j ^^ j^^, ^, —J, -^j -|-, -J, -14. — Prisms, ?^|j 



5 5 3 5. 



2^, If. Also -f J -f t - 1 > 5^tr >tjTjtl5¥9T^?f?^?^1 



1^, IS r^, IS is -2s -2^, los f^, -is -is is iS i^ t s i^. 



JL3 24 17 _5l — U-*^ -X"^^ -4^ -5"^ -8"^ -^4 -4"^ -f^"^^ 43 -U-^ • 



2 3 JJL 1J_ 1_L J^ 2.1 



y ". tV ^ > i^. 2 S -is -J ' , -f S "6^S Faces of composition 0, h R. 



Pyrites [p. 54, and I] —Twins of pyrites of Traversella, etc., figured and de- 

 scribed by Q. Sella in Studii sulla Min. Sarda, Turin, 1856. 



— iPyro 



>mi, 



Jalirb., 1856, 136. 



PvROMELANE [Suppl III] .—According to Shepard (Shepard's Min., 3d edit., 25>3), 

 B.B. infusible, but turns black and becomes opaque. It is soluble in the fluxes with 

 the reaction of titanic acid and iron. [The statement as to the composition given 

 by Prof Shepard (•* essentially a tifcanate of alumina and iron with traces of lime 

 and glucina? with zirconia?") is not deducible from any reactions published by the 

 author. — dJ 



Pyrochlore fp, 345, and IH. — Analysis of the fluo-pyrochlore of Miask by Her- 

 mann (J. f pr, Ch., Ixviii, 96):— Sb 4C15, Cb 14-68, Ti 4-90, Ce,Ea 15-23, y 0-94, 

 Je 2-23, Ca 9*80, Slg 1-46, K 0-54, Na 2-69, F 2-21=100-S3. 



Quartz fp, 145, and II, III] — Waumann has given in Leonk u. Bronn, 1856, p. 

 146, a review of the crystalline forms of Quartz determined by Descloizeaux, sub- 

 stituting his own symbols. They are as foUows [see Min. 145, and figs. 344, for 

 positions of planes.] 



1. Rhomhohedrom. -J, f, 1, |^, |, f , ^, f, |f, |, jg, 4^ j^i ^^ ^^ j^i 2, J, 



3, 4, V-, ¥, 5, V. 6, V, 8, 10, 13, 20, 50, -30, -17, -11, -10, -8, -7, -6, 

 -5, -¥-, -4, -h -¥, -3, -¥-, -¥, -h -h -¥, -2, -\S -I -h -h 



— 23 _Z _i. _A —S. _9 _1 -1 



TB"' 6' 3' ¥' 5» ^f ■^» 2' 



2. Trigonal Pyramids. |-2, 1-2, 2-2. 



3. Trigonal Trapezohedrons, or gyroidal forms. 



1. In the zone -1, 2-2, i.—{l) below 2-2 (all positive), 36-|f, 24-24 18-|f, 



12-if, 9-f, 6-f, 5-1, 4-f, ^I^-J/- ; (2) above 2-2 (all negative), j/-V-, |-f, 

 V-¥, f -f, f-i f -f, f -f, ^-i, f -f, ^-V-, if -if, i^ii ; also planes 



2. In the zone R, 2 2, t.— (1) below 2-2, (all negative); f-J-ff, ^-'h 

 12-if , 22-e, 28-ff. (2) Above 2-2 (all positive) ; ^ - V^, ^-^. f "f. I" t. 



¥-V, if -if, if -if ; also 1-f, 1-f. 



4. Trapezohedrons, beveling the obtuse or acute edges ofi?. l-5j 1--^, ^'f' 



5. Prisms 00 (on); oo-2 under a trigonal form ; and also the ditrigoual prisms 

 (replacing edges of t) oo-g, oo*|^, oo-J, oo-f, oo-^, OO'V? ^"Vj ^-^^? <3=-H^ 



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