MINERALOGY (by haplology for *mineral ology, from mineral, (II. mineral. Fr, mineral, from mineral!, ore, from minera. mineria, minaria, mine, from azincrarins, pertaining to mines, from minarc, to mine, lead and there, Lat. to drive. from ntioari, to threaten, from mime, threats, front minere, to jut out -Xoy/a, -/ogia, account, from /egrin, to say). The science of those natural substances known as minerals which. together or separately, form the material of the earth's crust. and also, as far as our kmon9tdge extends, that of other celes tial bodies. A mineral is a substance of definite chemical composition which has been directly produced by the processes of inorganic nature. It must be homogeneous even when submitted to minute inieroscopie examination, and must pos sess a definite composition capable of being ex pressed by a cheinival formula. Laboratory and furnace products, or such substances as shells and bones of animals, cannot be included in the range of mineralogy. It is the finict ion of the mineralo gist to investigate the form. properties, and com position of minerals; their genesis: their rela tions to one another, and to the accompanying rocks: the places where they are found: and t he geological conditions Under ogie1l I hey are formed.
of mineralogy is of importance to in hi, study of the rock formations, to the mining engineer in his search for metal produeing minerals, and to the metallurgist in the extraction of metals from minerals. :Many of the useful arts ;ire direetly dependent for their raw materials upon minerals, while some mineral species (teem- in such brilliancy and beauty of color as to be highly prized as gents.
Tux Pdt,txcilEs IINERAl.00y. The general subject of mineralogy may be divided into four sections: (1) Crygla llogru ph y, which includes the description of crystals. their charaeter, clas
sification, the mathematical relations of their faces and the methods of expressing them graphi cally and symbolically. (See Caysrma,omuellY.) (2) Physical mineralogy, Which describes the physical characters of minerals and deals With the properties related to their molecular struc ture. (3) Chemical mineralogy, which has for its object the determination of the chemical com position of each mineral species and the relation in composition between species in the same chemi cal group. (4) Descriptire mineralogy, which includes the detailed of each mineral species with respect to its form, structure, physi cal properties. chemical composition, and geo graphical and geological occurrence. The division of physical mineralogy is replete with interest ing problems of cohesion, optics, heat, and elec tricity. and suggests to the investigator along physical lines many fields for research. The problems connected with chemical mineralogy, while covering a narrower and less varied field than those of physical mineralogy, are none the less replete with interest. To the chemist work ing in the field of belongs the task of determining the part played by the various ele ments which enter into the composition of the hundreds of mineral species, many of which are rare and exceedingly complex in composition; the phenomena of isomorphism and dimorphism, and the chemical alteration of mineral species under the action of natural agencies, which is known as pseudomorphism.