Elementary Crystallography |
Other editions - View all
Common terms and phrases
albite atoms axes of symmetry axial planes axis of rotation-twinning basal pinakoid 001 beryl class Calcite centre of symmetry Chap clinopinakoid corresponding face crystal crystallising crystallographic axes cube cubic system cyclic number D.Sc diagonal planes digonal axes dihexagonal ditetragonal edges eight faces four faces Geology gonal goniometer h₂ h h₂ h₁ half-turn axes hemi-orthodome hemi-pyramid holoaxial indices intercepts inverse axis inversion-twin lateral axes Ludgate Circus metry minerals models monoclinic negative number of faces octahedron octant olivine one-third-turn orthoclase orthopinakoid orthorhombic orthorhombic system parallel parameters Plagioclase plane of symmetry planes of sym positive direction postage 5d principal axis prism projection pyramid quarter-turn quartz rhomb rhombic rhombohedron right angles rotation scalenohedron second order shown in Fig spinel class symbol symmetry at right tetra-trigonal tetragonal tetrahedron three axes Trapezohedron triclinic trigonal trigonal axis twelve faces twin-axis twin-crystal twin-plane twinning uniterminal usually vertical axis ΟΙΟ հլ
Popular passages
Page 23 - Consists of those crystals which have one axis at right angles to the other two, which are not at right angles to each other ; when transparent, they are optically biaxal ; as oxalic acid.
Page 119 - ... has no symmetry, different twin-laws give different results. In the presence of a centre of symmetry an axis of rotation-twinning is an axis of reflection-twinning. An axis of rotation-twinning lying in a plane of symmetry has at right angles to it in the same plane an axis of reflection-twinning. If the normal to a plane of symmetry be an axis of rotation-twinning, or if a line of symmetry (axis of even symmetry) be an axis of reflection-twinning, the same result may b*> obtained by the complete...
Page 135 - The authors are to be congratulated for having stated the essentials of Crystallography in such simple, clear language." — Journal of Geology. GRAPHICAL AND TABULAR METHODS IN CRYSTALLOGRAPHY. By TV BARKER. University Lecturer in Chemical Crystallography, Oxford. 14s. net, postage jd.
Page 37 - Stereographic projection the eye is supposed to be placed on the surface of the sphere at E (Fig.
Page 25 - Since p, q and r are rational pa qb re pqr their reciprocals h,k,l must also be rational and the law of rational intercepts may be re-stated as the law of rational indices in the following terms : if three axes are chosen parallel to three edges of a crystal which do not lie in one plane and if the intercepts on these axes of a parametral plane are a : b : c, then the intercepts of any other face of the crystal can be expressed as - : r : j where h, k and I HR It are whole numbers or zero.