A REVIEW OF THE AMORPHOUS MINERALS 529 



optically isotropic and usually structureless. As Cornu suggests, 

 these two forms should have distinctive names. He used limonite 

 for the crystalline mineral and stilpnosiderite for the amorphous 

 one, but in view of the fact that the simpler name limonite is so 

 well established for the common and widely distributed brown 

 hydrated iron ore of surface origin it seems advisable to retain the 

 name limonite for the amorphous mineral. Limonite in this 

 restricted sense has priority over stilpnosiderite, for it was used by 

 Hausmann in 18 13, while the name stilpnosiderite was introduced 

 by Ullmann in 18 14 and usually has been used as a varietal name 

 for eisenpecherz. 



A new name is necessary for the crystalline mineral with the 

 composition Fe 4 He0 9 , but in view of the fact that the mineral 

 hydroxids of irod are being investigated by the Geophysical 

 Laboratory no suggestion is offered at present. 



The melanosiderite of Genth is not an iron silicate, but limonite 

 with dissolved or adsorbed silica. The water content of the amor- 

 phous ferric oxids is variable, and so it is probable that xanthosider- 

 ite, limnite, and esmeraldaite are not definite hydrates, but are all 

 simply varieties of limonite. 



Stibiconite. Sb 2 4 (H 2 0) x (stibianite, stiblith, stibioferrite, vol- 

 gerite). — -The most common alteration product of stibnite is the 

 amorphous mineral stibiconite. It is probably colloidal antimony 

 tetroxid with adsorbed or dissolved water and not a definite hydrate. 

 The existence of crystalline antimony tetroxid is doubtful, for no 

 accurate description of cervantite has ever been made. Tenne and 

 Calderon state that much of the supposed Spanish cervantite is 

 valentinite. 



Cliachite. A1 2 3 (H 2 0) X (bauxite in part, wocheinite, sporogel- 

 ite, alumogel, shanyavskite) . — bauxite should be used as the name 

 of a certain type of rock and not as a mineralogical term. It was 

 so regarded by Dufrenoy, who introduced the name in 1845. He 

 has been followed by Tucan, Tschermak, and Lacroix. Dittler and 

 Doelter, however, use bauxitite for the rock name. 



The principal constituent of bauxite is an amorphous mineral 

 called cliachite (kliachite) by Cornu, who revived the name used by 

 Breithaupt. 



