ORDER VIII. PYRAMIDAL MANGANESE- ORE. 417 



Combinations. 1. |P 4. P. Fig. 105. 

 2. |P 4. P 1. P. 



Cleavage, P oo rather perfect ; P 1 and P 



less distinct, and interrupted. Fracture uneven. 



Surface, f P 4, very smooth and shining, P 



horizontally streaked and often dull. 

 Lustre imperfect metallic. Colour brownish-black. 



Streak dark reddish- or chestnut-brown. Opake. 

 Hardness = 5-0 ... 5-5. Sp. Gr. = 4-722, of a 



crystallised variety. 



Compound Varieties. Twin-crystals : Axis of 

 revolution perpendicular, face of composition par- 

 allel to a face of P 1. Fig. 106. The com- 

 position is often repeated parallel to all the faces of 

 the pyramid. Fig. 107. Generally small particles 

 only of the surrounding individuals are joined to 

 the central one. Massive : composition granular, 

 firmly connected. 



OBSERVATIONS. 



1. The pyramidal Manganese-ore consists of oxide of 

 manganese, but no analysis of it has yet been published. 

 Perhaps the variety from Piedmont, analysed by BERZE- 

 LIUS, which yielded oxide of manganese 75'80, silica 13-17* 

 oxide of iron 4'14, and alumina 2-80, may belong to the 

 present species. In the oxidating flame of the blowpipe 

 it yields a fine amethyst coloured glass. It is soluble in 

 heated sulphuric acid, -. , : 



2. It has been found in veins in porphyry, along with 

 other ores of manganese at Oehrenstock, near Ilmenau in 

 Thuringia, and at Ihlefeld in the Hartz. From these lo- 

 calities at least it seems to be a rare mineral. 



VOL. ii. 2 D 



