340 Review of Alger's Phillips^ Mineralogy, 



nearly equal dimensions in the opposite direction, or they are some- 

 times even in low flattened prisms. The secondary planes on the 

 edges incline on M, at an angle of 130° 5', and towards each other, at 

 142° 10', as determined by the reflective goniometer, by M. Dufrenoy, 

 of the School of Mines in Paris. Ledererite was discovered by Dr. 

 Jackson and the editor, between Cape Split and Cape Blomidon, Nova 

 Scotia, in the cavities of amygdaloid, accompanied by calcareous spar, 

 mesotype, analcime and stilbite. It has become a very rare mineral, 

 and is no longer found at the locality." 



There seems to be no sufficient reason for supposing the phos- 

 phoric acid, detected by Mr. Hayes, essential to this mineral. 

 According to Rammelsberg, its chemical formula differs from that 

 of gmelinite only in presenting one third as much water. The 

 inclination of the pyramidal planes on M, in gmelinite, according 

 to Rose, is 130° 27', which is near the same angle in Ledererite, 

 as above given. 



The new mineral Pyrrhite is stated on pp. 625, 626, to have 

 been recognized among some minerals brought from the Azores 

 by Prof. Webster ; the following is the account of it. 



Pyrrhite. 



" This exceedingly rare and beautiful mineral, hitherto found only 

 in Siberia, and of which but a single specimen comprising eight crys- 

 tals, is known to mineralogists, has been recognized among the inter- 

 esting substances recently brought from the Azores, by Prof. J. W. 

 Webster. The specimen was placed in Mr. Teschemacher's hands 

 for examination by Prof. Webster, and was supposed, by both of these 

 gentlemen, to be a new substance. On comparing it with pyrrhite, as 

 described at page 176, Mr. Teschemacher was at once convinced of its 

 identity with that substance. He has furnished the following descrip- 

 tion. Form, beautifully perfect regular octahedrons ; color, deep 

 orange-yellow ; transparent on the edges, with a brilliant vitreous lus- 

 tre. Hardness equal to that of feldspar. The crystals are from one 

 half to two lines in length, and they are superimposed on a white feld- 

 spar, or albite. The minutest crystals are quite transparent. One of 

 these exposed to the oxidating flame of the blowpipe, became opake, 

 retaining its orange color, but duller. Changed to the reducing flame, 

 it melted without frothing, and assumed a deep, dull indigo-blue color, 

 which could only be distinguished from black in a bright light, and on 

 the minute edges of the fused crystal. With borax, it melts into a 

 dark brown glass, apparently colored by iron. 



" It is probable that the mineral contains some titaniate, and that the 

 blue color almost instantly assumed by the assay, is owing, as Kersten 



