Intelligence and Miscellaneous Articles. 557 



NOTICES OF NEAV LOCALITIES OF RARE MINERALS, AND REASONS 

 FOR UNITING SEVERAL SUPPOSED DISTINCT SPECIES. BY 

 FRANCIS ALGER, MEMBER OF THE BOSTON SOCIETY OF NATU- 

 RAL HISTORY*. 



Phacolite from New York. 



This rare mineral, which comes to us principally from Bohemia 

 and Ireland, I have discovered among a suite of specimens of various 

 kinds found on New York Island, near Harlem, by Messrs. Mathews 

 and Johnson, of New York city. The specimens, which eventually 

 proved to he this mineral, were labelled stilbite ; but their appear- 

 ance was so peculiar, that I questioned at the time whether they 

 had been correctly designated, and determined to examine them 

 carefully at my earliest convenience. I have since received two 

 other specimens, better characterized than the first, from Mr. 

 Johnson. The crystals are in a geode form, implanted on calcareous 

 spar, and associated with silver-coloured mica and a few scales of 

 oligisto-magnetic iron ore. They are of a wax or honey-yellow co- 

 lour, have a waxy lustre, and the smallest individuals are translucent. 

 They are brittle, breaking with an uneven fracture, have none of the 

 foliated structure of stilbite, and afford no indications of cleavage. 

 Hardness superior to that of stilbite, and equal to that of chabasite. 

 Their surfaces are roughened or pitted, so as to reflect no image by 

 which they could be subjected to measurement by the goniometer. 

 Before the blowpipe, a fragment of the mineral swells and intumesces 

 slightly, like the Bohemian and Ferroe chabasite, and fuses into an 

 opaline, blebby bead ; at the moment of ignition, in the outer flame, 

 it gives out a beautiful green phosphorescence, which I have also 

 noticed, in a less degree, in the phacolite from Ireland. It is soluble 

 in hydrochloric acid. The crystals, at first sight, appear to be 

 rounded, and to have no determinate form ,- but, on closer examina- 

 tion, some of the smaller and more isolated ones are found to be 

 nearly perfect double six-sided pyramids, precisely similar to the 

 phacolite from Bohemia, differing from it only in colour and lustre. 

 I cannot doubt that, like that mineral, they are secondaries to a pri- 

 mary rhombohedron, probably of the same measurements, and are 

 also identical with it in composition. The absence of well-defined 

 cleavage is unfortunate, but this is a defect which applies equally to 

 the foreign mineral. Nor is the rhombohedral cleavage of ordinary 

 chabasite, of which phacolite is by many supposed to be only a va- 

 riety, by any means easily determined ; in fact, Sir David Brewster 

 has suggested, from optical investigations, whether the primary form 

 of chabasite be not a prism. 



Is Phacolite a variety of Chabasite, or distinct from it ? 



Tamnau of Berlin, in his very complete little essay on Chabasites, 

 has given very good reasons for uniting the two ; while Breithaupt 

 has maintained them to be distinct. The primary rhombohedron of 



* From the Journal of the Boston Society of Natural History. 



