Table 46. 

 ELASTICITY OF CRYSTALS. 



75 



Some particular values of the Elastic Moduli are here given. Under E are given moduli for extension or compression 

 in the directions indicated by the subscripts and explained in the notes, and under T the moduli for torsional 

 rigidities round the axes similarly indicated. Moduli in grams per sq. cm. 



(a) Isometric System.* 



Authority. 



Fluorspar 

 Pyrite . 

 Ruck salt 



Sylvine . 



Sodium chlorate 

 Potassium alum . 

 Chromium alum 

 Iron alum . . . 



1473 X 106 

 3530 X 10'^ 

 419 X 106 

 403 X 10^ 

 401 X lo^ 

 372 X io« 

 405 X io<5 

 iSi X 106 

 161 X 10*' 

 186 X iqS 



1008 X 10^ 

 2530 X 10'' 

 349 X io« 

 339 X 106 

 209 X 10" 

 196 X 10^ 

 319 X io« 

 199 X iqi* 

 177 X 10^ 



910 X lo^ 

 2310 X 10^ 

 303 X 106 



345 X 106 



1075 X 108 



129 X lo^ 



655 X io'5 



Voigt.t 



Koch.t 



Voigt. 

 Koch. 

 Beckenkamp.§ 



(l>) Orthorhombic System. 



Substance. 



Barite 

 Topaz 



E, 



620 X lo^ 

 2304 X lo^ 



E, 



540 X 106 

 2890 X 106 



959 X 106 

 2652 X 10^ 



376 X iqO 

 2670 X 10^ 



702 X 106 

 2893 X 10" 



740 X lo^ 

 3180 X 106 



Authority. 



Voigt. 



Substance. 



Barite 

 Topaz 



T,, = T,, 



283 X 10*5 



1336 X lo^ 



Ti 3 — T3 



293 X 10^ 

 1353 X 106 



T.., = T,„ 



121 X lO^ 



1 104 X 10^ 



Authority. 



Voigt. 



In the MoNOCLiNic System, Coromilas (Zeit. fiir Kryst. vol. i) gives 

 Emax = 887 X 106 at 21.9° to the principal axis. 

 E„i„=: 313X106 at 75.4° 

 Emai^ 2213 X 10^ in the principal axis. 

 Emin = 1554 X 106 at 45° to the principal axis. 



Gypsum 

 Mica 



In the Hexagonal System, Voigt gives measurements on a beryl crystal (emerald). 

 The subscripts indicate inclination in degrees of the axis of stress to the principal axis of 

 the crystal. 



Eo= 2165X106, E45 = 1796 X 106, E9o=23i2X io«. 



To = 667X106, T9o= 883X106. The smallest cross dimension of the 

 prism experimented on (see Table 82), was in the principal axis for this last case. 



In the RhombohedRAL System, Voigt has measured quartz. The subscripts have the 

 same meaning as in the hexagonal system. 



£0=1030X106, E_45 = 1305X106, E+45 = S5oXio6, £90 = 785X106, 



To = 508 X 1 06, T90 = 348 X 106. 

 Baumgarten 1[ gives for calcite 



Eo= 501X106, E_45 = 44i X106, E + 45 = 772Xio6, £90 = 790X106. 



* In this system the subscript a indicates that compression or extension takes place along the crystalline axis, and 

 distortion round the axis. The subscripts i and c correspond to directions equally inclined to two and normal to the 

 third and equally inclined to all three axes respectively. 



T Voigt, " Wied. Ann." 31, p. 474, p. 701. '»»? i 34i P- Q^i, 1888 ; 36, p. 642, 1888. 



t Koch, " Wied. Ann." i!S, p. 325, 1882. 



§ Heckenkamp, "Zeit. fiir Krvst." vol. 10. ^ u . .u , f ..t,.^^., 



II The subscripts i, 2, 3 indicaie that the three principal axes are the axes of stress; 4, 5. 6 inal the axes ot stress 

 are in the three principal planes at angles of 45° to the corresponding axes. 



H Baumgarten, " Pof;g. Ann." 152, p. 369, 1879. 



Smithsonian Tables. 



