- nthe ground mass or matrix of banded coal in which vitrain and, commonly, fusain layers as well, are embedded or enclosed.DISCUSSION — Layers in banded coal, often referred to as bands, are commonly 1 to 30 mm thick. Attrital coal in banded coal is highly varied in composition and appearance, its luster varying from a brilliance nearly equal to that of the associated vitrain to nearly as dull as fusain; it exhibits striated, granulose, or rough texture. In a few cases, relatively thick layers of such attrital coal are found that contain no interbedded vitrain. Nonbanded coal also is attrital coal but is not usually referred to as such. In contrast to the coarser and more variable texture of attrital coal in banded coal, nonbanded coal is notably uniform and fine in texture, being derived from size-sorted plant debris. The luster of attrital coal, which ranges from bright (but less than that of associated vitrain) to dull, is commonly used to describe and characterize attrital coal. As an alternative, some petrographers subdivide attrital coal into clarain and durain. Clarain has bright luster and silky texture, being finely striated parallel to the coal bedding. Durain has dull luster and sometimes is referred to as dull coal. Similarly, coal consisting of vitrain or clarain or a mixture of the two is sometimes referred to as bright coal.
ASTM D121-09a Standard Terminology of Coal and Coke. 2014.
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coal — n a brown to black combustible sedimentary rock (in the geological sense) composed principally of consolidated and chemically altered plant remains. DISCUSSION Conditions required for formation of coal are believed to include accumulation of… … Coke&Coal Terminology
attrital — ə.ˈtrīd.əl, a.ˈ , ītə adjective Etymology: Latin attritus + English al : of or relating to matter that has been worn by attrition attrital coal … Useful english dictionary
banded coal — n coal that is visibly heterogeneous in composition, being composed of layers of vitrain and attrital coal, and, commonly, fusain … Coke&Coal Terminology
nonbanded coal — n consistently fine granular coal essentially devoid of megascopic layers. DISCUSSION Nonbanded coal may be interbedded with common banded coal, or form a discrete layer at the top or at the bottom of the seam, or may compose the entire seam. It… … Coke&Coal Terminology
Petrologic components in coal and their groupings — ▪ Table Petrologic components (macerals) in coal and their groupings maceral grouping in Europe macerals maceral grouping in the United States name in Europe* name in the United States** vitrinite telinite megascopic anthraxylon attrital… … Universalium
lithotype — n 1) (1) Rock form defined on the basis of certain selected physical characteristics. (2) One of the four macroscopically recognized constituents of banded coal: vitrain, clarain, durain and fusain. D4596 2) any of the constituents of banded coal … Coke&Coal Terminology
vitrain — n shiny black bands, thicker than 0.5 mm, of subbituminous and higher rank banded coal. DISCUSSION Vitrain, attributed to the coalification of relatively large fragments of wood and bark, may range up to about 30 mm (approximately 1 in.) thick in … Coke&Coal Terminology