1892.] Mineralogy and Petrography. 247 



structure. Sanidine phenocrysts, augite, anorthoclase aud leueite lie 

 iu a ground mass of sauidine, nepheline and the other above-mentioned 

 constituents. 



Mineralogical News.— New Minerals.— Xcu-tonite and Rec- 

 ton'te.— Messrs. Brackett and J. F. Williams' >n_^v-t that tin- kaolin- 

 ite group of minerals consists of four members, each containing one 

 part of A1 2 3 , two of Si0 2 , and one, two, three and four molecules 

 of water respectively. The best-known of these are kaolin, with the 

 composition A1 2 3 2SiO,+2H 2 0, and halloysite, with an additional 

 quantity of loosely combined water. The places of two other mem- 

 bers they fill with the new minerals, newtonite and rectorite. The 

 former occurs in lumps in a clay associated with the shales and sand- 

 stones of the Barren Coal Measures on Sueed's Creek in Arkansas. 

 It is a pure white, soft, compact, infusible suhstanee, with a density of 

 2.37. It is only slightly soluble in boiling HC1, but is easily decom- 

 posed by hot H^O, and by boiling NaOH. Under high powers of the 

 microscope it appears to form rhombohedrons. Its analysis, calculated 

 for the pure dry material, yielded SiO, = 40.88 ; A1 2 3 = 35.85 ; 

 Loss, 23.27 = A1 2 3 2Si0 2 + 4H 2 0. Kectorite is found in veins in 

 sandstone in the Blue Mountain District, about twenty-four miles 

 North of Hot Springs, Ark. It is in soft white plates, closely resem- 

 bling mountain leather. Its hardness is less than that of talc, and it 

 is infusible. Upon heating it becomes brittle. The analysis, corrected 

 for impurities, gives SiO„ = 54.67 ; A1 2 3 = 37.22 ; Loss = 8.02 ; or, 

 if the excess of silica be regarded as an impurity, Si0 2 = 49.99 ; 

 ALO, = 41.16; H,0 = 8.84; besides 8.78% of H,0 at 110°-115°. 

 This corresponds tothe first place in the series, viz.: Alp 2Si< > 

 H 2 + Aq. The index of refraction for the substance is low. It 

 possesses two cleavages inclined to each other, and its acute bisectrix 

 is normal to one of these, p v. The crystallization is thought to be 

 monoclinic. Tested in the kiln the substance shows properties qufte 



different from those of kaolin. Plumboferrite.—The discovery of 



this mineral was announced by Igelstrom as long ago as 1881, but 

 since it has not been noticed in journals outside of Sweden the dis- 

 coverer reannounces his discovery in a recent article in German. 

 The mineral belongs to the franklinite group, from the other r 

 of which it differs in containing lead in place of zinc ~ * 



'ZtUs./. Kryst, xix, p. 167. 



