78 NEW YORK STATE MUSEUM 



Georgia and in Dutchess and Columbia counties, N. Y. 1 It is 

 also found in Richmond co. N. Y. 



Limonite is an abundant but low grade ore of iron; the ocher- 

 ous varieties are ground for paint. 



Bauxite AL0 3 .2H 2 



Bauxite is a hydrous aluminium sesquioxid containing 73.9$ 

 alumina and 26.1$ water. The aluminium is often replaced in 

 part by iron. Bauxite occurs in disseminated, rounded grains 

 and in oolitic, spongy or claylike masses; sometimes fine grained 

 compact. The luster is dull and the color varies from white 

 when pure to red, yellow, and brown for the iron-bearing 

 varieties. 



Bauxite is found at Baux and elsewhere in France; also in 

 Arkansas, Alabama and Georgia. It is the chief source of 

 aluminium and is used in the manufacture of alum. 



Brucite MgO.H 2 



Brucite is the magnesium hydrate and contains 69$ magnesia 

 and 31$ water. 



The crystals are rhombohedral and tabular in habit. The 

 mineral is of more frequent occurrence in translucent foliated 

 masses and in fibrous forms. The luster is pearly or waxy to 

 vitreous and the color white, gray, bluish or green. 



Brucite occurs in serpentine and limestone associated with 

 other magnesium minerals. It is found at Hoboken N. J., at 

 Brewster, Putnam co. and in Richmond and Westchester coun- 

 ties N. Y.; also at Texas Pa. 



Gibbsite AL0 3 . 3H 2 



Gibbsite is an aluminium hydrate containing 65.4$ alumina 

 and 34.6$ water. 



It is rarely found in six sided monoclinic crystals, but usually 

 occurs in mammillary crusts and stalactitic shapes (pi. 24J 

 which sometimes show an ill defined, fibrous, internal structure. 

 The color is commonly white or nearly white but may be grayish, 

 greenish, reddish or yellow; the luster is subvitreous. The 

 mineral is found in small deposits, often associated with linion- 



*N. Y. state rnus. Bui. 7. 1SS9. 



