Abstract
The Knoop hardness of vitrite, exinite-durite, mineral-durite and coaly shale of various coal seams in Kayanuma coal field (Hokkaido, Japan) has been measured.The hardness of macerals decreases in the following order: coaly shale, mineral-durite, exinite-durite and vitrite.The hardness of coaly shale and mineral-durite depends on their mineral contents.The relation between hardness and carbon content of various Kayanuma vitrites is similar to that between hardness and rank of ordinray Japanese coals, but the former shifts to lower hardness under 90 per cent carbon content and higher hardness over 90 per cent carbon content.It is supposed that Kayanuma vitrites are metamorphosed under the special geological condition, because the coal band of Kayanuma vitrites shifts to the richer hydrogen region than that of ordinary Japanese coals.
