MINERAL SURVEY FOR PIEZO-ELECTRIC MATERIALS 



151 



8?S 



I 



I 



15 



32?I 



5 



I 



32?I 



8?I 



M 



5 



2 



I 



I 



*10I 



5 



MI 



I 



I 



17 



I 



Wollastonite 



Wulfenite 



Wurtzite 



Xanthoconite 

 Xanthophyllite 

 Xanthoxenite 

 Xenotime 



Yttrialite 



Yttrocerite 



Yttrofluorite 



Yttrokrasite 



Yttrotantalite 



Zeratite 



Zaophyllite 



Zeunerite 



Zincite 



Zinkenite 



Zinwaldite 



Zircon 



Zirkelite 



Zoisite 



Zorgite 



Zunyite 



5 



*10 



*20A 



21 

 5?I 

 5?S 



15 



M 

 M 

 32 



M 

 I 



15 



*19?I 



8 



5 



15 



32 



8 



M 



*31AS 



Of the 830 minerals listed 70 belong to classes that allow piezo-activity 

 but only 17 are found to be active by the Giebe and Scheibe test. (Our test 

 of lodyrite was negative but Greenwood and Tomboulian'* found it to be 

 active; on the other hand, we found Scolecite to be active while they report 

 it inactive.) It may be that others of the remaining 56 classes have such 

 small piezo-electric constants as to be undetectable. Others may be in- 

 correctly classified as to symmetry. 



Of these active materials, quartz is the most important. Because of its 

 excellent mechanical properties (stability, etc.) as well as for its relative 

 cheapness it seems destined to remain one of the most important piezo ma- 

 terials. 



Tourmaline is also important because of the high magnitude of its elastic 

 moduli in certain directions; however, it cannot be obtained in large pieces 

 of satisfactory homogeneity. 



Sphalerite is very difficult to handle because of its many cleavage planes, 

 and appears to give little promise of becoming practically useful. Its activ- 

 ity is quite marked. 



Homogeneous crystals of calamine appear to be very rare, so that work- 

 able crystals large enough for ordinary piezo-electric application are un- 

 obtainable. Most of the material occurs massive. 



On Piezo Electricity — Greenwood and Tomboulian — Zeits. f. Krist. Jan. 1932. 



