and iShepard^s Treatise on Mineralogy. 339 



" There is a slight deficiency in the quantity of soda, but this salt 

 evidently consists of one atom sulphate of soda, one atom sulphate of 

 lime. This is the composition of the variety from Villa Rubia, in 



Spain, originally analyzed by Brongniart. Formula : NSl-j-CalSl, or 



as stated by Mr. Hayes, NaS-f-CaS. 



" It occurs in extremely brilliant, colorless and transparent crystals, 

 imbedded in hydrated borate of lime, or Hayesine. They are in the 

 form of elongated oblique rhombic prisms, simply replaced on their 

 obtuse terminal edges, by single planes." 



The Ledererite of Dr. Jackson, which Mr. Alger retains as a 

 distinct species, is described as follows, on pages 214, 215. 



Ledererite. 

 w C. T. Jackson. {Am. Jour, of Hci., Vol. xxv, 78.) 



" This mineral is composed, according to the analysis of A. A. 

 Hayes,* of silica, 49-47; alumina, 21-48; lime, 11-48; soda, 3-94 ; 

 phosphoric acid, 3-48 ; oxide of iron, 0-14 ; water, 8-58. 



"Sp.gr. 2-10. H.znG. 



" It occurs in crystals which are sometimes colorless and transparent, 

 but usually white and opake, or only translucent on the edges, some of 

 them being of a pale salmon color. The crystals are in the form of 

 hexahedral prisms, deeply replaced on their terminal edges, or termi- 

 nated at both extremities by hexahedral pyramids, having at their sum- 

 mits a small plane termination, perpendicular to the axis of the prism ; 

 indicating a regular hexahedral prism for the primary form. This 

 form is further indicated by the separation of faces of cleavage made 

 visible by exposure to heat. Before the blowpipe, according to Hayes, 

 it becomes white, and divides at the natural joints ; at a higher tempe- 

 rature it fuses into a white enamel, which can be rendered more vitreous 

 by continuing the blast ; a few bubbles are disengaged when it is thus 

 treated. In the matrass, a slight empyreumatic odor is perceptible. 

 Its inferior hardness and specific gravity, but more especially its py- 

 rognostic characters and chemical composition, clearly separate it from 

 the species hydi-olite, or gmelinite, to which it has been referred : one 

 consisting of bisilicates of alumina and lime, silicate of soda, with six 

 per cent, phosphate of lime, and only 8-58 water ; the other, by Mr. 

 Connell's analysis, of bisilicate of alumina, tersilicate of lime, soda and 

 potash, no phosphoric acid, and 21-66 per cent, water. 



" Some of the crystals are elongated, and measure one third of an 

 inch in the direction of the prismatic axis, but most of them possess 



* Am. Jour, of Sci., Vol. xxv, p. 84. 



