126 Chronicles of Science. [Jan., 



The new mineral is to be called Polyargyrite or Weichglaserz. It 

 occurs in small iron-black crystals, belonging to the cubic system, 

 and consisting of 12 AgS -j- SbS 3 . Now that we are acquainted 

 with another member of these antimonial sulphides, it may be well 

 to compare the composition and crystalline system of these minerals, 

 since it is hardly probable that another species of this group will be 

 found containing more silver- sulphide than is present in polyar- 

 gyrite. 



Miargyrite . . . . Ag S + Sb S 3 . . . . oblique 



Pyrargyrite 



Stephauite 



Polybasite 



Polyargyrite 



Argentine 



3 Ag S + Sb S 3 . . . . hexagonal. 



6 Ag S + Sb S 3 . . . . rhombic. 



9 Ag S + Sb S 3 . . . . hexagonal. 



12AgS + SbS 3 .. .. cubic. 



A°rS cubic. 



Another new mineral from the same locality is described under 

 the name of Wolfachite. It crystallizes in the rhombic system, and 

 contains :— Ni S 2 + Ni (As 2 Sb 2 ). 



English ears will not easily get reconciled to the sound of 

 Wollongongite — the name which Professor Silliman proposes for 

 a new native hydrocarbon, which promises to become of great 

 technical importance.* It seems to be a variety of cannel, occurring 

 abundantly in the Wollongong district of the Illawarra coal-field 

 in New South Wales. On distillation it yields a large volume of 

 gas of remarkably high illuminating power. 



A mineral mistaken for augite has lately been found by Pro- 

 fessor Brush to be a new variety of chrysolite, and he has accordingly 

 named it Rortonolite, in recognition of Mr. Silas Horton's courtesy 

 in calling his attention to it.f It occurs in the form of dull blackish 

 rhombic crystals, in the iron mine at Monroe, Orange Co., New 

 York ; and from its abundance it may become of some commercial 

 importance as an iron-ore. It is chemically a chrysolite, containing 

 iron, magnesia, and manganese. 



Among the fine pebbles of stream- tin from Durango, in Mexico, 

 it is well known that the mineralogist finds the most beautiful little 

 crystals of limpid topaz. With these there have lately been 

 detected certain oblique crystals of an orange-coloured mineral, 

 which Professor Brush names after the locality.:]: The following 

 is the general formula of Durangite, where the protoxides are soda 

 and manganous oxide, whilst the sesquioxides are alumina and 

 ferric oxide : { J (3 K 0) -f- f (B 2 3 ) } As 5 . Fluorine is also 

 present in this mineral, but its quantity has not been determined. 

 It is said that Durangite is the only native " fluo-arsenate " which 

 has hitherto been observed. 



Professor Brush has also lately published the analysis of a 



* Silliman's ' American Journal of Science,' July, 1869, p. 85. 

 f Ibid., p. 17. % Ibid., Sept., 1869, p. 179. 



