Geology and Mineralogy. 261 



lar planes. Some of the crystals are tapering at the ends and the 

 basal plane is thus obliterated. The crystals with basal plane 

 are generally dull, being coated with an opaque film, suggesting 

 incipient alteration. Cleavage indistinct, basal. The tapering 

 crystals from - 5-l mm thick and up to 5 mm long, the opaque from 

 0*5-2 mm thick and 2-3 mm long. Color white ; luster vitreous, in- 

 clining to greasy. B.B. in a closed tube, gives no water ; decrepi- 

 tates and gives an abundance of sublimed lead chloride, soluble in 

 water, leaving a yellowish white oxychloride. Easily soluble in 

 dilute nitric acid. 



Composition = PbO . 2PbCl„. 



The analyses gave : 



1. 2. 



Tapering crystals. Opaque crystals. Calculated 

 CI = " 18-55 17-94 18-21 



Pb = 78-25 lost. 79-73 



O = 2-06 



100-00 



Associated with the Penfieldite is a mineral in long (up to 10 mm ) 

 silky needles, which largely volatilizes on heating, and may be 

 another form of Penfieldite, or a new mineral ; the other associ- 

 ates are anglesite and small quantities of laurionite. 



Philadelphia, July 26th, 1892. 



9. Brief notices of some recently described minerals. — Masrite 

 is a fibrous kind of alum found in Upper Egypt and described by H. 

 Droop Richmond and Hussein Off. It contains a small amount 

 of cobalt and, as believed by the authors, a minute quantity of a 

 new element for which the name masrium is proposed, after the 

 Arabic name for Egypt. Assuming that masrium is a bivalent 

 element, its atomic weight is calculated as 228, and it is regarded 

 as belonging in the beryllium-calcium group in which group there 

 is a place in the periodic system for an element with an atomic 

 weight of 225. The analysis of masrite gave: 



S0 3 A1 2 3 Fe,0 3 X* MnO CoO FeO H 2 Insol. 

 36-78 10-62 1-63 0-20 2"56 T02 4"23 40-35 2'61 = 100 



a X=Masrium oxide. — Proceedings Chem. Soc, April 21, 1892; 

 Nature, May 26. 



Basiliite is a hydrous manganese antimonate described by 

 Igelstkom from the Sjo mine, Grythytte parish, Sweden. It 

 occurs in steel-blue bladed forms with metallic luster, which it 

 loses upon exposure ; it is not magnetic. An analysis gave : 



100-01 



For this the formula 1 lMn o 3 • Sb 2 0. . 2lH o is calculated. — 

 Geol For. Fork., vol. xiv, 307, 1892. 



Sb 2 5 



Mn 2 3 



Fe.,0 3 



H 2 



13-09 



70-01 



1-91 



15-00 



