74 



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Feldspar 

















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3 

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cd 

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s 









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1 



59 



7 



2 



70 



12 



3 



64 



14 



4 



67 



8 



5 



59 



12, 



6 



67 



7 



7 



38 



14 



9 



44 



8 



10 



53 



14 



II 



55 



12 



13 



43 



12 



И 



40 



5 



15 



57 



7 



16 



63 



7 



17 



53 



4 



18 



69 



11 



19 



50 



12 



22 



46 



13 



23 



50 



14 



24 



56 



12 



25 



52 



20 



26 



59 



8 



27 



55 



14 



28 



55 



11 



29 



54 



8 



30 



51 



21 



31 



52 



13 



32 



30 



18 



33 



25 



23 



34 



49 



16 



35 



36 



17 



36 



19 



11 



37 



16 



5 



40 



14 



3 



41 



10 



4 



42 



33 ! 



4 



43 



48 



16 



45 



55 



11 



46 



56 



15 



1 



9 



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6 



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1 

 1 



less double-refraction, but there does not exist any convenient 

 way to distinguish between them in rounded grains of sand. 

 The consequence is that the numbers given for these minerals, 

 especially for the olivine , which is always found in small 

 quantities, must be considered as rather inexact; the total 



