Third Supplement to Dana's Mineralogy. 255 



Galactite [Suppl. i, n]. — Tn the author's 1st supplement (this Journal, May, 

 1855), he pointed out that the analysis of galactite by von Hauer gave the formula 

 of natrolite, whence, he concluded, that galactite is probably natrolite. Authentic 

 specimens of the mineral have since been examined by Dr. Heddle (Phil. Mag. [4], 

 xi, 272), and the composition of natrolite obtained in each case. The following 

 (1, 2, 3) are his results, together with analyses of related specimens : 



Si £l Ca Na H 



1. Glenfarg, white, 48 24 27 00 0 82 14-82 9 24 = 100 12 



2. " red, 47-84 27-112 4 312 11 304 1024 = 100 808 



3. Campsie Hills, 47 324 27 36 2 63 13 354 10 392= 101 060 



4. Bishoptown, white, 47 60 26 60 016 15-86 9 56 = 99 78 



5. " pink, 47 76 27 20 0-93 1428 9 56 = 99 72 



6. Bowling, near ? 48 . 033 2 5 261 2 313 13 975 9 723 ¥>e0 865, Stg 0-403 =100 573 



Kilpatrick, \ ° 



7. Dumbarton Moor, 46 96 26-908 3 76 12-83 9-50 = 99 958 



Galena [p. 39, 506, and Suppl. i, n]. — A galena containing 8'7 p. c. of sulphur, 

 and also 51 30 of sulphate of lead has been observed at Neu-Sinka, Siebenburg, and 

 described by R Hofmann. This mechanical mixture has been called super-sulphu- 

 retted lead and also Johustonite. Jahrb. k. k. geol. Reichs., 1855, 1. 



Garnet [p. 190, and Suppl. I, it]. — An analysis of the green garnet which occurs 

 in brevicite on the island of Stokoe in the Brevig Fiord afford Dr. D. Forbes (Edinb. 

 N. Ph. J. [2], iii, Jan. 1856): 



Si A 1 ! Mn Ca Mg JSTa & loss 



L 34 96 8-73 20 55 240 3209 trace 127 



2. 33 84 9 18 20-31 3192 trace 



3. 23 94 30 14 



The results correspond to the formula, as Dr. Forbes states, (-£Ca 3 -f-jS'e) Si=Ca 8 

 'Si-f-F^ Si=3ilica 35 61, lime 32 98, sesquioxyd of iron (alumina) 31 "41 =100, whence 

 the mineral is identical in composition with melanite, notwithstanding its color. 

 The crystals lie together, forming 6 sided prisms, or are distinct rhombic dodecahe- 

 drons. Color fine leek-green. G. (from 76 crystals at 60° F.) 3'64. 



A Melanite from the Kaiserstuhl afforded Schill (G. Leonh. Min. Badens, 1855, in 

 N. Jahrb. 1855, 838): 



li 3tl Ca % Fe Mn 



45-80 11-00 22- 10 2-00 18 25 7-70 == 9985 



[In Suppl. ii, under Garnet, for Bi read Si.] 



Gilbertite [p. 223]. — E. Zschau states his opinion that Gilbertite at Graupen is 

 derived from topaz, where it occurs associated with topaz, tin ore, fluor, apatite and 

 quartz, in gneiss ; and the same he regards as probably true of the gilbertite of Al- 

 tenberg, Ehrenfriedersdorf, etc. — (Letter to G. J. B., as under Urdite.) 



Glaserite [p. 365]. — According to Scacchi (op. cit., p. 186) this sulphate of pot- 

 ash, which is not common at Vesuvius, was rather abundant at the eruption of 1848, 

 and occurred sparingly in that of 1855. 



Guano. — Prof. C. U. Shepard has given names to different portions of the har- 

 dened or "petrified" guano of Monk's Island, in the Caribbean Sea (Am. J. Sci., [2], 

 xxii, 96) calling them collectively pyroguanite minerals. He remarks that the guano 

 has " been subjected to the agency of heated trap rock, whereby the greater portion 

 of it has been thoroughly fused." [The guano overlies and incrusts trap. But this 

 appearance of fusion is merely a result of the consolidation and concretion through 

 infiltrating waters. The same kind covers unhardened guano. — j. d. d.] 



The tuberose and reniform massive guano material of a grayish white to brown- 

 ish color, he has named pyroclasite, the name alluding to its flying to pieces when 

 heated. H.=4. G.=2 - 36 — 2 4. " It consists of not far from 80 p. c. of phosphate 

 of lime and 10 p. c. of water; while the remainder is made up of a little insoluble 

 matter, carbonate of lime, sulphate of lime, sulphate of soda and traces of chlorid 

 of sodium and fluorine." [The analyses by others give varying results.] 



