Table 87 

 ELASTICITY OF CRYSTALS 



139 



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* 



Substance. 



Authority. 



Fluorite . , 

 Pyrite . . 

 Rock salt . 



Sylvite . , 



Sodium chlorate 

 Potassium alum . 

 Chromium alum 

 Iron alum . . . 



1473 X io b 

 3530 X io b 

 419 X io 6 

 403 X io 6 

 401 X io 6 

 372 X io 6 

 405 X io 1 ' 

 181 X io 6 

 161 X io 13 

 186 X to 6 



1008 X io 6 

 2530 X io 6 

 349 X io 6 

 339 X io 6 

 209 X io 6 

 196 X io 6 

 319 X io 6 

 199 X io 6 

 177 X io 6 



910 X io 6 

 2310 X io 6 

 303 X io 6 



345 X io 6 



1075 X io 6 



129 X io 6 



655 X io 6 



Voigt.t 



Koch.t 



Voigt. 

 Koch. 

 Beckenkamp.§ 



(b) Orthorhombic System 



Substance. 



Barite 

 Topaz 



620 X io 6 

 2304 X io 6 



E, 



540 X io 6 

 2890 X io 6 



959 X io 6 

 2652 X io 6 



E, 



376 X io 15 

 2670 X io 6 



702 X io 6 

 2893 X io y 



740 X io 6 

 3180 X io 6 



Authority. 



Voigt. 



Substarrce. 



Barite 

 Topaz 



T 12 = T 2 , 



283 X io 6 

 1336 X io 6 



Tk 



293 X io 6 

 1353 X io 6 



T,, = T, 



121 X IO 6 



1 104 X io 6 



Authority. 



Voigt. 



In the Monoclinic System, Coromilas (Zeit. fiir Kryst. vol. 1) gives 

 C r> um 1 E mai = 887 X io 6 at 21.9 to the principal axis. 



1 E min = 313x106 at 75-4° 

 ,,■ ( E m „ = 2213 X io 6 in the principal axis. 



I E min = 1554 X io 6 at 45 to the principal axis. 



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. 



E = 2i65Xio 6 , E 45 = 1796 X io 6 , E 90 = 2312 X io fi , 



T = 667Xio 6 , Tgo= 883 X io 6 . The smallest cross dimension of the 



prism experimented on (see Table 86), 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. 



E =iO3oXio 6 , E_ 45 = 1305 X io 6 , E +4 5 = 85oX io 6 , E 90 =785X10", 



T = 508 X 1 o 6 , T 90 = 348 X io 6 . 

 BaumgartenH gives for calcite 



E =5oiXio 6 , E_45 = 44i X io 6 , E +45 = 772 X io 6 , E 90 = 79oXio 6 . 



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

 distortion round the axis. The subscripts b 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, 1687; 34, p. 981, 1888; 36, p. 642, 1888 



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



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



il The subscripts 1, 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. 



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



Sn"i t hsonian Tables. 



