128 Fourth Svpphment to Danas Mineralogy. 



The red Galaciiie of Glcn-farg analyzed by Dr. HeJJle [see our 2(1 Suppl.], he re- 

 ferred in liis former paper to natrolite. But like the mesolite it is intermediate be- 

 tween natrolite and scolecite in containing both soda and lime, lR=|^]S"a+iCa [ap- 

 proximately], and a slight excess of water above that in natrolite, and he proposes 

 for it the name Farqite. 



The oxygen ratio for R, B, Si, H, in natrolite is 1 : 3 : G : 2 and lE^lNa; for 



Fargite, 1 : 3 : 6 : 2^, and lK=iCa+|-N'a; for Mesolite 1 : 3 : 6 : 2 J and ifi^jCa-f 



iXa; for Scolecite 1 : 3 : 6 : 3, and lfi=:i:lta, there being an apparent increase in the 

 water, from 2 to 3 in the ratio, with the increase of the lime. [The analyses of Dr. 

 Heddle vary but little from what the scolecite oxygen ratio (1 : 3 : 6 : 3j requires; 



(i^a+fCa)Si+XlSi+3fl:=silica 46-25, alumina 25-71, lime 9 35, soda b'll, water 

 13*52=100. The water exceeds that of analysis 1 by 0'69 ; of 2, by 0-6 ; of 3, by 

 0-48.1 



The Antrimolite of Thomson is shown by the analyses to be Mesolite, and not to 

 contain potash, as Thomson's analysis states. 



Senarmontite [p. 140]. — Tlie octahedral oxyd of antimony occurs in the district 

 of Haractas, Algeria, along with antimony glance (from whose decomposition it has 

 resulted), antimonious acid, and some galena. It is slightly arsenical, and this may 

 accouni for its taking the octahedral form, since oxyd of arsenic is usually octahe- 

 dral- ^ These minerals are also mixed with calcite, cerusite, and red antimony, which 



likewise are a result of modern changes. Fouruet, Bull. G«ol. Soc. France, 1855, 

 xii, 1039. 



Serpextine [p. 282, 511, and I, II, IIIJ.— The following note on Antigorite has 

 been communicated for this Supplement by Prof. G. J. Bru^h. 



Analysis of Antigorite, by Geo, J. Brush. — In the 1st Supplement allusion is made 

 to the fact that Schweizer has announced that his analyses of antigorite arc inaccu- 

 rate and should tlierefore be rejected. He states (Fogg, xcii, 495) that from recent 

 examinations made in connection with Stocker-Escher, the loss of weight by heat in 

 two trials was 13*30 and 13*26 p. c., while in his early analyses the amount of water 

 was given as 3*70 p. c.; farther, he says that Stocker-Escher is engaged in making 

 a complete analysis of the mineral which in due time will be made public. 



As some three years have elapsed since this announcement was made, and so far 

 as I can learn, no analysis has been publislied, it may not be out of place here to 

 give an analysis that I had occasion to make of this raineral some months since. 



The specimen analyzed was obtained from Dr. Krantz. Its physical properties 

 and blowpipe reactions are identical with those given by Schweizer. The mineral 

 V^as decomposed by carbonate of soda in the usual manner, and special precautions 

 were taken to ensure a complete separation of the magnesia from the iron. The 



analysis gave : 









gi 



fe 



■kg 



^i,€r 



41-58 



n-2'2 



36-80 



trace 



SI a 



' 2-60 12-67 



4 



This is the chemical composition of serpentine, and antigorite may be considered 

 therefore as one of its slaty varieties. 



Serpentine marbles. — Chemical examination by C.T. Jackson, this Journ., xxiii, 123, 



Stassfurtite [Suppl. Ill, under Boeacite].— Analysis by 0. F. Chandler (Inaug. 



Dissert); B 69-18, iiig 29-93, Fe 0-89, Ca ;race=100, proving its essential identity 

 in composition with boracite. 



Stjlpnomelane [p. 287 and III], — A mineral whose characters, as far as can be 



gathered from the description, approach those of Stilpnomelane, ha^ been described by 

 Shepard (Shep. Min., p. vi) undrr the name oi Rastolyte. It resembles a mica, and 

 occurs in an oblique prism, 0:7=98°, plane angle of base 120^. Crystals J to IJ 

 inches across. Parallel to foliated; also cleavages I and a diagonal. Color ash-grey, 

 rtfddish; bluish on the diagonal cleavage. Brittfe, Yields water and fluorine. B.B- 

 becomes grayish-black and fuses to a black magnetic globule. A trial, admitted to 



be approximative only, gave, Si 42 30, it 38'25, 3tl 650, Ca 2*00, Jig I'OO, fi and F 

 8-80, alkali and loss (with some oxygen for part of the iron as peroxyd) 6'15=:100. 



