Anthracite Mohs scale), its higher relative density of 1.3–1.4, and luster, which is often semi-metallic with a mildly brown reflection. It contains a high percentage of fixed carbon and a low percentage of volatile matter. It is also free from included soft or fibrous notches and does not soil the fingers when rubbed. Anthracitization is the transformation of bituminous coal into anthracite. The moisture content of fresh-mined anthracite generally is less than 15 percent. The heat content of anthracite ranges from 22 to 28 million Btu per short ton (26 to 33 MJ/kg) on a moist, mineral-matter-free basis. The heat content
A-class destroyer (1913) tons and had a length of around . All were powered by triple expansion steam engines and had coal-fired water-tube boilers (although initially, some had "locomotive type" fire-tube boilers in lieu). Armament was generally one QF 12 pounder on a bandstand on the forecastle, up to five QF 6 pounder and 2 single tubes for torpedoes. The "Daring" and "Havock"-class ships initially had a third tube in the bow, fixed to fire straight ahead, but this was found to weigh down the bows and it was possible for the ship to run over its own torpedo when moving at high