South Mountain Mining District, Idaho. 125 



I. Ilvaite, Golconda Mine, South Mountain, Idaho. Anal. 



by W. F. Hillebrand, U. S. G. S. Bull. 591, p. 318. 

 11. Ilvaite, Potter Cr., near Baird, Shasta Co., Cal. Anal. 



by W. B. Moss, this Journal, 26, 14, 1908. 



III. Ilvaite, Barclay Sound, Vancouver Id., B. C. Anal, by 

 Hoffman, this Journal, 42, 432, 1891. 



IV. Ilvaite, Greenland. Anal, by Lorenzen, Min. Mag., 5, 

 63, 1882. 



V. Ilvaite, Elba. Anal, by Early, Proc. Irish Ac, 3, 52, 



1877. 

 VI. Ilvaite, required by formula, H.,0.2Ca0.4FeO.Fe„0 3 .- 

 4Si0 2 . 



Other Properties. — In the ilvaite from Idaho, traces of 

 cleavage are occasionally observed parallel to 010. This 

 is very indistinct and no other cleavage was observed. 

 The fracture is uneven; H. 5.75; G. 4.059 (Hillebrand) ; 

 luster vitreous, and not sub-metallic as described from 

 other localities ; color black ; streak black with very faint 

 inclination toward brown. The mineral is rather diffi- 

 cultly fusible before the blowpipe. Intumesces slightly 

 and yields a black magnetic bead. Readily soluble in 

 hydrochloric acid giving an amber solution which gelati- 

 nizes upon cooling. 



Several unsuccessful attempts were made to cut ori- 

 ented sections of the crystals. The material is too 

 opaque to transmit sufficient light to show the optical 

 properties in the thinnest sections which could be ground. 

 In rock or ore sections of the ordinary thickness (±.03 

 mm.) this mineral would be perfectly opaque and anhe- 

 dral grains might easily be mistaken for magnetite. It 

 is therefore suggested that ilvaite may be present in fine- 

 grained aggregates of contact-metamorphic minerals and 

 have a much wider distribution than has hitherto been 

 suspected. 



West Haven, Conn. 



