Britl/h M'tneralogical Society, 365 



, Its perpendicular fradlure is ftraight or fliglitly waved 

 fibrous, difcoveriiig an obfcure fine Tlratification parallel lo 

 the direftion of the whole ftratuni : hence the varying or 

 chatoyant lultre is obferved only when moving it in the di- 

 reftion of the fibres. The ciofs or parallel fraAure requires 

 a ftronger blow to etfcifl it than the former, and prefents a 

 compact, broad, fi)lintcry furface. 



When broken, it flies into flattened fibrous fragments. 



In thin pieces it is femi-traniparent. 



Can juit be fcratched by the nail : is brittle: non-elaftict 

 fp. gr. 3-709 to 2721. It may be pqliflied to almoft a mirror- 

 like furface, and is then exquifitcly beautiful. 



Its proper place in a niineralogical arrangement feems to 

 be between compaft Ilalaclite {dicbtcr kJkJintcr), and flaty 

 fpar {Jchicferjpath). 



Analyjis of the Satin Spar, by Mr. H. Pfpjs junior. 

 Preliminary Experiments. 



A piece of about 400 grains was expofed to a red heat for 

 two hours. It loll: near i-4th of its weight, and was much . 

 altered in its appearance, having loll its fmooth feel. Upon 

 imnierfion in water, it imbibed it with a hifling found, be- 

 came hot, fell to powder, and a portion of it was diflblved. 

 The folution was rendered turbid by carbonic acid. The 

 undiflblved portion eflfervefced fliglitly with acids, and had 

 obtained an hepatic fmell from fome adhering pyrites. 



A portion of the crude fpar, carefully freed from all ad- 

 hering pyrites, diflblved completely in nitric acid, with effer- 

 vefcence. This folution was examined with the following 

 re-agiuits: 



On adding fulphuric acid to a portion of the folution, the 

 two fluids hecan)c nearly folid, and much heat was extri- 

 cated ; proving the prelence of Iniie, flrontian, or barvtcs. 



Strontian water gave a precipitate of a brown colour, 

 ■which was again foluble in nitric acid. 



Barytic water gave a precipitate of rather a darker hue than 

 the Itrontian : this was alio foluble in the nitric acid. 



Tincture of galls, prufliate of potafli, and ammonia, gave 

 flight traces of the prelence of iron. 



A folution of fuiphate of foda gave the fame granulated 

 precipitate as with a folution of niirnle of lime. 



100 grains of the picked fatin fpar were expofed to the 

 aAion of 200 grains of nitiic acid of fp. gr. 1-25 in a veflel 

 of a conical torni furnillied with a fmall glals worm on the 

 top, that, Oiould any fluid be carried up hv the gafeous pro- 

 du(.H, it might be depofiled in its pafl.igc. Thi.s and the vcllel 



were 



