Examination of Hyalosiderite, a new Mineral. 185 



with the crystals of slags, formed in various metallurgic pro- 

 cesses, we find a corresponding similarity not only°in the 

 forms in general, but also in the angles of inclination of the 

 planes. The measurement of these angles, which M. Haus- 

 mann has given in his Specimen CrystallographiceMetallurgica:, 

 §32, could be but very imperfect on account of their small 

 size. The determinations here communicated, which cannot 

 indeed boast of very great accuracy, will contribute to adjust 

 rn some measure the determinations published in that treatise. 

 The rectangular octahedron described by M. Hausmann 

 (fig. 14, 15, 16)^ is formed by the planes which are here 

 marked d and r'; the planes d answer to the planes M, chosen 

 in the definition of that treatise ; so that the planes r' corre- 

 spond with the planes P. Later observations have also ac- 

 quainted us with the planes d' in the crystallized slag. The 

 rectangular bases of the rectangular octahedrons in the cry- 

 stallized slag, namely in that from the copper pyrites smeltinc 

 works at Lauten (Hausm. Spec. Cryst. Met. fig. 18), answer 

 perfectly to an octahedron formed by the bounding planes d' 

 and d. The angles which the diagonals of the rectangular 

 bases form with their edges, are similar to the semi-angles of 

 the base of the ground form, consequently = ^CB'B and 

 ^.CBB'. These angles measure, according to the funda- 

 mental proportion ol inclination above assumed, 55° 35' 3" 

 and 34° 24' 57". 



II. Chemical Analysis. 

 § 9. 



The hyalosiderite brought to a red-heat, whether in a glass 

 retort or in a platinum crucible, becomes black, but does not 

 yield any perceptible quantity of water; nor is it perceptibly 

 altered in texture or in weight. 



Concentrated muriatic acid attacks the mineral even when 

 cold, dissolves it by the aid of a gentle heat, and forms with 

 it, on evaporation, a gelatinous mass, which after desiccation 

 was evidently silica. 



a.) A few decigrammes of the powdered mineral were now 

 treated with concentrated muriatic acid, until their solution 

 was completely effected ; the solution evaporated to dryness 

 by a gentle heat; the residuum extracted by water, acidulated 

 with the same acid, and separated by a filter. The yellowish 

 fluid thus obtained was mixed with caustic ammonia, which 

 produced a reddish-brown precipitate. This was again dis- 

 solved in muriatic acid, in order to ascertain whether mag- 



Vol. 63. No. 311. March 1824. A a nesia 



