GUIDE TO THE MIXERALOGIC, COLLECTIONS 



77 



The luster is adamantine and the color yellowish, reddish and 

 blackish brown. 



Gothite occurs with other oxids of iron specially hematite 

 and limouite and is classed commercially with limonite under 

 the name of " brown hematite." It is an ore of iron. 



Manganite Mn 2 0..H 2 



Manganite is a hydrated sesquioxid of manganese containing 

 27.3jl oxygen, 62.4^ manganese and 10.3^ water. 



Manganite occurs in orthorhombic crystals usually prismatic 

 with deeply striated or grooved surfaces; these are frequently 

 grouped in bundles giving the appearance of sheaves of rods 

 (pi. 23J. It is rarely found in massive granular or stalactitic 

 forms. The luster of manganite is submetallic and the color 

 gray to black. i 



Manganite occurs associated with other manganese minerals 

 which commonly result from its alteration. 



For uses see Pyrolusite. 



Limonite (brown hematite) 2Fe 2 3 .3H 2 



Limonite is a hydrated sesquioxid of iron differing from 

 gothite in the relative amount of iron sesquioxid and water; 

 it contains 25.7^ oxygen, 59.8 r < iron and 14.5^ water. The 

 ocherous varieties often contain clay or sand. 



Limonite does not occur crystallized. It is commonly found 

 in mammillary, botryoidal or stalactitic masses grading into 

 loose and porous bog ore and earthy and concretionary masses. 



The compact variety has a black varnishlike surface and 

 fibrous radiated structure (pi. 23 2 ). The forms of looser struc- 

 ture are characterized by a dull luster and range in color from 

 brown to yellow. The streak of limonite is brown. 



Limonite is formed from the decomposition or alteration of 

 other minerals containing iron; thus the bog ore is deposited 

 in a marshy place by streams carrying iron in solution which 

 is oxidized, sinks to the bottom, and in time by the combined 

 action of heat and pressure is transformed into a bed of 

 limonite. 



Limonite is found in Bavaria and other parts of Germany, in 

 Scotland, Sweden, etc. It is mined from large deposits in 

 Virginia, Alabama, Pennsylvania, Michigan, Tennessee and 



