See also:matter, the
See also:physical and chemical properties of which are the same about every point, may be either amorphous or crystalline . In amorphous matter all the properties are the same in every direction in the mass; but in crystalline matter certain of the physical properties vary with the direction . The essential properties of crystalline matter are of two kinds, viz. the general properties, such as
See also:density, specific
See also:heat, melting-point and chemical composition, which do not vary with the direction; and the directional properties, such as cohesion and
See also:elasticity, various
See also:optical, thermal and electrical properties, as well as
See also:form . By reason of the homogeneity of crystalline matter the directional properties are the same in all parallel directions in the mass, and there may be a certain symmetrical repetition of the directions along which the properties are the same . When the
See also:crystallization of matter takes place under conditions
See also:free from outside influences the peculiarities of
See also:internal structure are expressed in the external form of the mass, and there results a solid
See also:body bounded by
See also:plane surfaces intersecting in straight edges, the directions of which bear an intimate relation to the internal structure . Such a polyhedron Grows, many, espa,
See also:base or
See also:face) is known as a crystal . An example ofthis is
See also:sugar-candy; of which a single isolated crystal may have grown freely in a solution of sugar . Matter presenting well-defined and
See also:regular crystal forms, either as a single crystal or as a
See also:group of individual crystals, is said to be crystallized . If, on the other
See also:hand, crystallization has taken place about several centres in a confined space, the development of plane surfaces may be prevented, and a crystalline aggregate of differently orientated crystal-individuals results . Examples of this are afforded by
See also:loaf sugar and statuary marble . After a brief
See also:sketch, the more salient principles of the subject will be discussed under the following sections: I .
CRYSTALLINE FORM . (a) Symmetry of Crystals . (b)
See also:Simple Forms and Combinations of Forms . (c)
See also:Law of Rational Indices . (d) Zones . (e)
See also:Projection and
See also:Drawing of Crystals . (f) Crystal Systems and Classes . i . Cubic
See also:System . 2 . Tetragonal System . 3 .
Orthorhombic System . 4 .
See also:Monoclinic System . 5 . Anorthic System . 6 . Hexagonal System Regular Grouping of Crystals (Twinning, &c.) . Irregularities of Growth of Crystals: Characters of Faces . (x) Theories of Crystal Structure . II . PHYSICAL PROPERTIES OF CRYSTALS . (a) Elasticity and Cohesion (Cleavage,
See also:Etching, &c.) .
(b) Optical Properties (Interference figures, Pleochroism, &c.) . (c) Thermal Properties . (d) Magnetic and Electrical Properties .
ANTON CSENGERY (1822-1880)
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