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BISPHENOIDAL

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Originally appearing in Volume V07, Page 579 of the 1911 Encyclopedia Britannica.

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BISPHENOIDAL CLASS (Hemihedral). Here there are three dyad axes, but no planes of symmetry and no centre of symmetry. The See also:

general See also:

FORM (Lat. forma)

form {hkl} is a bisphenoid (fig. 61) bounded by four scalene triangles. The other See also:

SIMPLE

simple forms are geometrically the same as in the See also:

HOLOSYMMETRIC

holosymmetric class. Examples: epsomite (See also:

EPSOM

Epsom salts, MgSO4.7H20), goslarite (ZnSO4.7H20), See also:

SILVER

silver nitrate, See also:

SODIUM [symbol Na, from Lat. natrium; atomic weight 23.00 (0=16)]

sodium See also:

POTASSIUM [symbol K (from kalium), atomic weight 39.114 0=16)]

potassium dextro-tartrate (seignette See also:

salt, NaKC4H4O6.4H20), potassium antimonyl dextrotartrate (See also:

TARTAR

tartar-emetic, K(SbO)C4H406), and See also:

ASPARAGINE

asparagine (C4H8N203'H20). See also:

HEMIMORPHITE

Hemimorphite. 4. See also:

MONOCLINIC

MONOCLINIC 1 See also:

SYSTEM

SYSTEM (Oblique; Monosymmetric). In this system two of the angles between the crystallographic axes are right angles, but the third See also:

ANGLE (from the Lat. angulus, a corner, a diminutive, of which the primitive form, angus, does not occur in Latin; cognate are the Lat. angere, to compress into a bend or to strangle, and the Gr. ayKOS, a bend; both connected with the Aryan root ank-, to

angle is oblique, and the axes are of unequal lengths. The See also:

AXIS (Lat. for " axle ")

axis which is perpendicular to the other two is taken as 0Y =b (fig. 62) and is called the ortho-axis or ortho- See also:

DIAGONAL (Gr. &a, through, ywvia, a corner)

diagonal.

The choice of the other two axes is arbitrary; the See also:

VERTICAL (from Lat. vertex, highest point)

vertical axis (OZ =c) is usually taken parallel to the edges of a prominently See also:

DEVELOPED

developed prismatic See also:

ZONE (Gr. 'WV77, a girdle, from 'wvvLvay to gird)

zone, and the clino-axis or clino-diagonal (OX =a) parallel to the zone-axis of some other prominent zone on the crystal.. The acute angle between the axes OX and OZ is usually denoted as and it is necessary to know its magnitude, in addition to the axial ratios a: b: c, before the crystal is completely deter- See also:

MINED

mined. As in other systems, except the cubic, these elements, a : b : c and f3, are characteristic of the substance. Thus for See also:

GYPSUM

gypsum a : Iz : c=o•6899 : 1:0.4124; 0=80° 42'; for See also:

ORTHOCLASE

orthoclase a : b : c= 0.6585 : I : O•S554; $=63° 57'; and for See also:

CANE

cane-See also:

SUGAR

sugar a : b : c= 1.2595 : I : 0.8782; ft =76° 30'.

End of Article: BISPHENOIDAL

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