MARCASITE. Modern mineralogists, following Haidinger, have restricted this name to those forms of native bisulphide of iron which crystallize in the orthorhombic system, and are sometimes known as “prismatic iron-pyrites.” By the older mineralogists the word was used with less definite meaning, being applied to all crystallized and radiated pyrites, whether rhombic or cubic. In the last century both minerals were extensively used as ornamental stones. The marcasites were generally of small size, faceted like rose diamonds, and brilliantly polished, in which form they were mounted in pins, brooches, shoebuckles, watch-cases, and other ornamental objects. The lustre of the polished surface was so brilliant that the stone, although opaque, formed a rough substitute for diamond; and this lustre was not readily impaired by atmospheric influences. Much of the old marcasite jewellery is of so pale a colour as almost to resemble burnished steel; such kinds generally belong to the true modern marcasite, sometimes called “white pyrites ”; while the specimens which possess a brassy yellow colour are mostly referable to the cubic species, which is distinctively termed pyrite. Some of the finest pyrites suitable for the jeweller is found in Elba and in Brazil; but the mineral enjoys ä very wide geographical distribution, and is common in England, especially in Cornwall, where it is known to the miners as “mundic.” By the ancient Peruvians the mineral was extensively used for amulets, while the larger pieces were polished as mirrors; hence marcasite is sometimes called pierre des Incas. The word marcasite, variously written marchasite, marchesite, marque site, &c., appears to have been introduced from Spain, and is supposed to be of Arabic origin. It is notable that the ...