1813.'] 



Description of Lythrodes, 



III 



Article IIL 



Lythrodes : a new Species of Mineral from the North, 

 By D. L. G. Karsten.* 



Among the magnificent mineral products of Fridricbswarn^ ia 

 Norway, I have found a mineral, the properties of which will 

 be better known by the following description of its characters : — 



Colour. Aurora red, passing into brownish red : and in some 

 specimens through flesh red into yellowish brown and pale 

 brown : here and there with cream, yellow, and greenish spots. 



External aspect. Massive and disseminated. 



Lustre, In the principal fracture, resinous and glimmering; 

 in the cross fracture, without lustre. 



Fracture. Passing from uneven to splintery; but the texture 

 concealed foliated with several cleavages, which vrere only 

 ascertained after having examined a number of specimens. 



Fragments show a tendency to regularity. 



Distinct concretions. Granular, with a rough surface. 



Transparency, Opake^ or at most slightly translucent on the 

 edges. 



Streak, White. 



Hardness. Semihard in the greatest degree. 

 Frangibility, Pretty easily frangible. 



Specific gravity 2' b\0. Not particularly heavy. According 

 to an analysis of this fossil performed by Dr. John, by a method 

 which he will hereafter describe, its constituents are as follows : — > 



Silica 44*62 



Alumina 37-36 



Lime 2*75 



Soda 8-00 



Water 6-00 



Oxide of iron i -00 



Loss 0-27 



100-00 



There is no other mineral, among those already described, 

 which possesses tlie characters and yields the same constituents 

 as this, among which the proportions of soda and water are 

 the most remarkable. On that account I have placed it in the 

 system as a new peculiar species of mineral, belonging to the 

 genus of siliceous stones. 



* From the Gesellschatt NaturforscheDder freunde zu Berlin Magazin IS 10, 

 p. 7S. 



