PHYSIOGRAPHY. 



Andalusite. 



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Hardness = 7-5. Sp. gr. = 3'104 (of a cleavable va- 

 riety.) 



Compound varieties. Massive : composition indistinctly 

 granular and columnar. 



1. The mineral long known under the name of Made or Chiastolite 

 appears to be a mixed mineral, consisting of Andalusite and some of the 

 minerals entering into the formation of clay slate ; the Andalusite assum- 

 ing a crystalline form and being subject to a remarkable composition, 

 which will be understood from the annexed figures representing cross 

 sections of the twin-crystals. The twin crystal in each instance, it will 

 be seen, results from the juxta-position of four single crystals, whose 

 nearest point of contact, as respects any two of them, is formed by 

 Fig. 12. Fig. 13. Fig. 14. 





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20 



2* 



