Table 83. 

 ELASTICITY OF CRYSTALS. 



103 



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 tlie axes similarly indicated. Moduli in grams per sq. cm. 



(a) Isometric System.* 



Substance. 



Authority. 



Fluorite 

 Pyrite . 

 Rock salt 



Sylvite 



Sodium chlorate 

 Potassium alum . 

 Chromium alum 

 Iron alum . . . 



1473 X 106 

 3530 X 106 

 419 X 106 

 403 X 106 

 401 X 10^ 

 372 X lo*^ 

 405 X 10" 

 181 X 106 

 161 X I c^ 

 1S6X 106 



1008 X 10^ 

 2530 X io« 

 349 X io« 

 339 X loB 

 209 X lo** 

 196 X 10'' 

 319 X 10*5 

 199 X lot^ 

 177 X 106 



910 X lo^ 

 2310 X lo^ 

 303 X iqS 



345 X 106 



1075 X io<^ 



129 X lo^ 



655 X lo'^ 



Voigt.t 



Koch.J 



Voigt. 

 Koch. 

 Beckenkamp.§ 



(i) Orthorhombic System. I 



Substance. 



Parite 

 Topaz 



El 



620 X lo^ 

 2304 X 106 



540 X 106 

 2890 X lo^ 



959 X 108 

 2652 X 106 



376 X lo*^ 

 2670 X 10^ 



702 X 106 

 2893 X 10" 



740 X 106 

 3180 X 10^ 



Authority. 



Voigt. 



Substance. 



Barite 

 Topaz 



T,, = T2, 



283 X 106 

 1336 X 10" 



Ti 3 — T3 



293 X lo^ 

 1353X106 



T.., = T, 



121 X lO^ 



1104X lO^ 



Authority. 



Voigt. 



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

 Eojax^887 X lo^ at 21.9° to the principal axis, 

 f En,i„ = 3i3X 10'' at 75.4° " " " 



Emai = 2213 X lo^ in the principal axis. 

 Emin = 1554 X 10® 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. 



£0=2165X10^ E45= 1796X 10", £90=2312 X lofi, 



To ^667X10", T9o= 883 X lo*^. 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=1030X10", E_45= 1305X106, £4.45 = 850X106, £90=785X106, 



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

 Baumgarten 1[ gives for calcite 



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



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

 distortion round the axis. The subscripts 6 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, 18S7; 34, p. 981, 18SS ; 36, p. 642, 1888. 



t Koch, "Wied. Ann." 18, p. 325, 1882. 



§ Heckenkamp, "Zeit. fiir Kryst." vol. 10. 



II The subscripts i, 2, 3 indicate that the three principal axes are the axes of stress; 4, 5, 6 that the axes of stress 

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



II Baumgarten, " Pogg. Ann." 152, p. 369, 1879. 



Smithsonian Tables. 



