IS golb. Observations. Iron-pyrites is sometimes auriferous, but the richest varieties, at Facebay in Transylvania, do not afford more 0.02 to 0.03 of gold. Auriferous pyrites is also met with at Adelfors in Smoland in Sweden, in the Valais and Grisons in Switzerland, in Dauphiny, Siberia, and Mexico. This variety is distinguished from copper and iron pyrites, by colour, specific gravity, and malleability. 2. Electrum, or Argentiferous Native Gold. Electrum, Klaproth. 1 ' Electrum, Vlin. Hist. Nat. xxxiii. cap. iv. § 23.—Naturliches Electrum, v. Veltheim’s Grundriss einer Mineralogie Bruun- scher, 1781, fol. 11.—Elektrum, Klap. b. iv. s. 1.—Argenti ferous Native Gold, Aikin, 2d edit. p. 76. External Characters. Its colour is pale brass-yellow, passing into silver- white. It occurs in small plates, dentiform, and in imperfect cubes. The other characters arc not stated by Klaproth, to whom we are indebted for what is known of this mineral. Chemical Characters. It is not soluble either in nitrous or nitro-muriatic acids. Constituent