COMBUSTIBLE MINERALS, NOT GASEOUS. 191 



face of the ledge. On making an excavation, the coal widened to twenty-two inches ; but it 

 then diminished to a narrow seam, and the working was abandoned. This locality was about 

 a thousand feet above the Hudson. The coal is said to be light and shining, and it burns 

 with a moderate flame. Other veins of a similar kind have been noticed in the same range.* 



LIGNITE. 



[From the Latin lignum, wood; in allusion to its origin.] 



Lignite. Cleaveland and Beudant. — Wood Coal. TTumson. 



Description. This mineral, which is often described as a variety of coal, still difl'ers con- 

 siderably from it. All its varieties have undoubtedly originated from wood, and the process 

 of change has probably taken place at a period not very remote. In most cases the texture 

 of the wood is preserved, and it burns exactly as wood does, leaving a residue of ashes, but 

 often more abundant. 



The odour which lignite exhales is different from that of burning coal or bitumen. It is 

 usually unpleasant, sometimes sharp or fetid. It also differs from coal, in yielding, when 

 subjected to distillation, a peculiar acid liquor. 



Varieties. Jet. This is deep black, opaque, and so solid and hard that it may be turned 

 on a lathe. Fracture conchoidal. Lustre resinous. 



Brittle Lignite. Differs from jet, by its great brittleness. Colour black, with a shade of 

 brown. It is less shining than jet. The surface is easily divisible into cubical or trapezoidal 

 fragments. 



Bituminous Wood. This is made up of the roots, branches or trunks of trees, usually 

 somewhat compressed. Texture ligneous, with little lustre. Colour brown, or brownish 

 black. 



Composition. Carbon 71.71, hydrogen 4.85, oxygen and nitrogen 21.67, ashes 1.77 

 {Richardson and Regnault). 



Geological Situation. Lignite is usually found in the more recent formations. When 

 in sufficient abundance, it is converted to the same uses as coal and anthracite ; but this is 

 seldom the case. 



localities. 



Richmond County. Near Rossville is a stratum of hgnite from three to six inches thick, 

 near or below high water mark. Sometimes the mineral has the colour and appearance of 

 wood slightly charred ; at others, it is quite compact, has a dark brown or nearly black colour, 

 and resembles jet. Crystals of iron pyrites occur in the fissures of the lignite, and these are 



* J. Pierce. American Jounuxl of Science^ VI. 86, 



