NEW MINERALS. 279 



ore forms a belt or seam, and a considerable ([iiantitv of it mi<>lit be obtained 

 were the material in sufficient demand. 



Redingtonite — On tlic 150-f()ot Icvcl of tlic Hcdington, at a point where 

 solfataric gases still issne, a hydrous cbromium sulphate occurs in fissures 

 in silicified serpentine. This substance is doubtless the result of the action 

 of the gases upon clironiic iron. Qualitative analysis showed tliat it is a 

 hydrous sulphate of chromium, containing- some aluminium and iron prob- 

 ably replacing chromium. The mineral is a finely fil)rous mass, and some- 

 times the fibers are only just distinguishable under the microscope. The 

 color is pale purple. The aggregates of parallel fibers sometimes appear 

 white, excepting on the surface perpendicular to the fibers. Under the micro- 

 scope the mineral is colorless, tlie fibers are extremely fine, and no crystal 

 form is visible. The fibers possess double refraction and never extinguish 

 parallel to the nicol planes. The angles of extinction vary between 13° 

 and 38°. The crystals are therefore probably triclinic. It seems appropri- 

 ate to give the name redingtonite to this hitherto unknown mineral. 



When tin's mineral is heated it turns green without losing all its water, 

 and coatings of this green sulphate occur upon the redingtonite.' Under 

 the microscope this green sulphate is found to be composed of rhombic 

 tables with angles of 78° and 102°. The cleavage parallel to the base is 

 excellent, and it also possesses good cleavages parallel to the prism faces 

 and to the macropinacoid. It is somewhat pleochroitic, and the color is 

 most intense when the short diagonal is parallel to the principal nicol plane. 

 The refraction and tlie double refraction are of medium strength. The 

 mineral seems to be isomorphous with copiapite. The tables are too small 

 to show the emergence of the optical axes ; but tests with the mica foil 

 sliow that of the two axes of elasticity lying in the basal plane the one 

 parallel to the bracln'axis is the larger. This agrees with copiapite, which 

 is negative. The detection of these minerals is due to Mr. Lindgren. 



siucification. — Thcrc arc two distinct periods of silicification traceable at 

 Knoxville. One of these is represented by a fine net-work of quartzose 

 veins intersecting a groat proportion of the metamorpho.sed rocks. Silicified 

 shales or phthanites are particularly prominent in this respect; but altered 



