MINERALOGY, the science which describes and classifies the different kinds of mineral matter constituting the material of the earth's crust and of those extra-terrestrial bodies called meteorites. The study of minerals is thus a branch of natural history, but one in which certain of the exact sciences find an application. The determination of the composition and constitu tion of minerals is a chemical problem ; their optical and other physical properties are determined according to the principles of physics ; the study of their crystalline form and structure be longs to crystallography; their modes of occurrence, origins, associations and changes come within the province of geology and petrology; while a consideration of the localities at which they are found requires some acquaintance with geography. Finally, there is the economic side, dealing with the mining and application of useful minerals, the extraction of metals from their ores, and the uses of minerals for building, decoration and jewellery.
Many minerals have attracted the attention of mankind from the earliest times. The stone and bronze implements of prehistoric man and many of his personal ornaments and charms were directly or indirectly of mineral origin. The oldest existing treatise on minerals is by Theophrastus rEpi, TCov XiBc.ov—On Stones, c. 315 B.0 (Eng. version by John Hill, 1746), of which only a portion remains. Minerals were then classed as metals, stones and earths. The last five books of Pliny's Historia naturalis, written about A.D. 77, treat of metals, ores, stones and gems. Some of the Arabian philosophers devoted themselves to the study of minerals, and about 1262 Albertus Magnus wrote his De mineralibus. In the 16th century Georgius Agricola pub lished several large volumes, dealing more especially with the mining and metallurgy of metalliferous minerals, in which more exact descriptions were given of the external characters ; he mentioned several minerals by names (e.g. blende, fluor, quartz) which are now in common use. About the same period there appeared the systematic treatise on minerals of K. Gesner (1565), and that on precious stones by Anselm Boethius de Boodt (1609). The remarkable researches of Erasmus Bartholinus on
Iceland-spar were published in 1669, and J. F. Henckel's Pyritologia in 1725. Later came the Systema naturae of C. Linnaeus (1735). Although the importance of chemical proper ties was recognized by the Swedish chemists—J. G. Wallerius (1747) and A. F. Cronstedt (1758)—the external characters of minerals formed the basis of the mixed systems of classification of A. G. Werner (1774) and of other authors, and even as late as the Natural History System of Mineralogy of F. Mohs (1820).
It was not until the end of the 18th and beginning of the 19th century, when the foundations of crystallography were laid by Rome de l'Isle and R. J. flatly, and chemistry had assumed its modern phase, that any real advance was made in scientific mineralogy. It was then recognized that chemical composition and crystalline form were characters of the first importance, and that external (natural history) characters were often more or less accidental. During this period numerous mineral substances were analysed by Scheele, Berzelius and others, and many new mineral-species and chemical elements discovered. After W. H. Wollaston's invention of the reflecting goniometer in 1809, exact measurements of the crystalline forms of many minerals were made. The principles of isomorphism and dimorphism enunciated by E. Mitscherlich in 1819 and 1821 respectively cleared up many difficulties encountered in the definition of mineral-species. About the same time also the discovery by E. L. Malus of the polarization of light gave an impetus to the optical examination, by Sir David Brewster and others, of natural crystals. Later, the investigation of rocks in thin section under the microscope led to the exact determination, particularly by A. Des Cloizeaux (1867), of the optical constants of rock-forming minerals.
For a detailed account of the history of mineralogy (including crystallography), see F. von Kobell, Geschichte der Mineralogie von 1650-186o (Miinchen, 1864) P. Groth, Entwicklungsgeschichte der mineralogischen Wissenschaften (Berlin, 1926).