WARREN AND PALACHE. — QUINCY PEGMATITES. 



161 



composition of the compound Na2Fe2Si40i2 which is Si02 52 per cent 

 Fe203 34.6 per cent, Na20 13.4 per cent. 



Parisite. — The occurrence of the rare fluo-carbonate of calcium and 

 the cerium earths, parisite, as a pneumatolitic mineral in the Quincy 

 pegmatites is a new and interesting one. A closely related mineral, 

 synchisite, associated with the barium-parisite, cordylite, has been 

 described by Nordenskiold ^^ and Flink ; ^^ it occurs 

 at Narsasuk, Greenland, implanted on feldspar and 

 aegirite or in cavities in pegmatite, an occurrence 

 identical with that at Quincy. 



Parisite has been found both in the Ballou pegma- 

 tite where it occurs only as grains in the massive 

 rock, and in the Fallon pegmatite pipes where it is 

 relatively abundant in all parts of the pipe where 

 open spaces are present, implanted on the surfaces 

 of the microcline and aegirite crystals. It also is 

 found to some extent on the fragments in the central 

 pocket. The crystals of parisite are generally sharply 

 formed and of prismatic habit, ranging from ex- 

 tremely slender columns as much as one cm. long to 

 short, stout, prismatic individuals scarcely longer 

 than broad. The color is clear amber yellow in fresh 

 crystals, dull yellow to brown and opaque when 

 altered as it not unfrequently is. Such altered 

 crystals show a perfect basal cleavage and pearly Figure 5. 

 lustre on the base, both of which properties are entirely absent in fresh 

 material. The same dependence of cleavage upon chemical alteration 

 was found to exist upon parisite from Muso, the type locality, so that 

 cleavage is undoubtedly a secondary property in this mineral. 



The crystals are invariably striated horizontally and show infinite 

 variety in the detail of individual development. They are either tri- 

 gonal or hexagonal in cross-section ; in the former case steep rhom- 

 bohedrons being dominant, in the latter second-order pyramids. In 

 neither case are actual prism planes more than rudimentary, the 

 pseudoprisms being bounded by oscillatory combination of the steeply 

 inclined rhombohedron or pyramid faces. The termination is gen- 

 erally a large and brilliant lustrous face of the pinacoid ; sometimes, 

 however, the relative size of this plane is much reduced by the presence 

 of low rhombohedrons and second-order pyramids which either slightly 

 truncate the edges between base and pseudoprism or may be developed 



" G. For. Forh., 16, 338 (1894). 



" Bull. G. Inst. Upsala, 5, 81 (1901) ; Med. om. Gronland, 14, 236 (1898). 



