WARREN AND PALACHE. — QUINCY PEGMATITES. 155 



from impurities. This was broken up and carefully picked over by 

 hand under a powerful glass. When examined under the microscbpe 

 it appeared agreeably free from alteration and included grains, except 

 some inevitable black dust and a few black oxide particles as well as a 

 trace of aegirite and microcline. The average of closely agreeing dupli- 

 cates is given in column 1, Table I. For comparison a number of 

 analyses of riebeckite and crocidolite of similar composition from other 

 localities are reproduced in columns 2-10. Several others have been 

 omitted because their large content of MgO and CaO excludes them 

 from a close comparison with the present type. 



The Quincy mineral differs rather sharply from the Socotra variety 

 in the relative proportions of ferric and ferrous iron, the latter being 

 much higher in ferric and lower in ferrous oxide. The Colorado and 

 Cape Ann varieties (this last is from an alkaline stock similar in many 

 respects to the Quincy stock and distant from it some forty miles) are 

 much closer in this respec'., as is also that from Red Hill, although 

 this contains a notable quantity of CaO. The crocidolite analyses 

 (7-9) show a rather closer relationship to the Quincy mineral. The 

 alkalies of the Socotra and Colorado minerals are also notably higher 

 than those of the Quincy riebeckite which, however, is nearer to the val- 

 ues for these oxides in the case of the Cape Ann and Red Hill mineral 

 and in all of the crocidolites. The water percentages are not satisfac- 

 tory, and at least in the case of crocidolite undoubtedly represent in part 

 hydroscopic water. Fluorine is probably present in all. With correc- 

 tions made in the waters and fluorine the agreement in the analyses 

 would probably be closer. For further comparison the molecular ratios 

 derived from the above analyses are given in Table H. 



TABLE II. 



Nos. 1 2345678 9 10 



SiO, 0.863 0.833 0.822 0.830 0.820 0.756 0.868 0.865 0.869 0.850 



FejOs + 0.097 .177 0.192 0.093 0.123 0.105 0.137 0.120 0.122 0.111 



a little AI2O3 



TiOj 0.015 .. .. 0.017 



RO, chiefly 



FeO 0.337 0.176 0.168 0.278 0.326 0.391 0.262 0.296 0.299 0.300 



NasO -f- a little KjO 



0.111 0.148(0.150)20.149 0.123 0.108(0.098)20.125 0.101 0.103 

 H2O +F 0.0821 0.089' .. 0.0833 0.128^0.2173 0.200 



1 H2O above 115°. 2 By difference. 



3 Total, probably loss on ignition and therefore high. 



If the TiOa is deducted, with a proportionate amount of FeO to form 

 ilmenite, the ratios for the Quincy riebeckite (No. 1) may be appor- 



