SYLVAN, in mineralogy, a genus which is divided into four species ; 1. "The native sylvan," of which the colour is intermediate between tin white and silver white : it occurs massive and dis seminated, and also in various kinds of crystals : internally it is shining, and its lustre is metallic : its specific gravity is from 4.1 to 6.1. Its constituent parts are, Sylvan 92 55 Iron 7.20' Gold • 0 25 100 Before the blow-pipe it melts as easily as lead, emits a thick white smoke, and burns with a light green colour, and a sharp disagreeable odour. When exposed to a low heat, it is converted into an oxide: by an increase of temperature, it melts into a brownish black glass, in. which gold grains are interspersCcl : at a still higher heat, the oxide is completely vola tilized. It occurs in veins, and is accompa nied with iron pyrites, blende lead-glance, quartz, and lithomarge, and is found in Transylvania. It bears a strong resem blance to antimony, and was formerly call ed " aururn problematicum :"—" white gold ore," &c. It was denominated " sylvan" by Kirwan, and is so called by Jameson, who thinks it inure expressive than " tellurium," a name proposed by Klaproth. • 2. " Graphic ore," which is likewise found in Transylvania : it is worked as an ore of gold, and has obtained the name of graphic gold : it consists of Sylvan 60 Gold 30 Silver . 10 100 It occcurs, in veins, in clay porphyry, ac companied with iron pyrites, grey copper ore, Mende, and sometimes, though rare ly, with native gold. Before the blow
pipe it burns with a green flame, and is volatilized.
3. " Yellow sylvan ore," which is white inclining to yellow, and is found dissemi nated and crystallized. Specific gravity 10.6. It dissolves in nitrous acid, and during the solution nitrous gas is evolved: the constituent parts are, Sylvan ..... . . . 44 75 Gold 26.75 Lead 19.5 Silver 8.5 Sulphur 0.5 100.
This is found in Transylvania, and is worked on account of the proportions of the silver and gold.
4. " Black sylvan ore," which is of an iron black colour, and occurs massive, and in small, thin, and longish six-sided tables : externally it is splendent, with a metallic lustre: and within it is shining : specific gravity is almost 9. Its constitu ent parts are, Sylvan 18.8 Lead 24.8 Gold 415 Silver 0.25 Copper 0.6 Sulphur Oxide of manganese . 9.2 Quartz 43.7 100.
It is found in Transylvania : it melts be fore the blow-pipe: the sulphur and syl van are soon volatilized, and a blackish brown globule remains, which being melted with borax, a sort of silvery gold grain appears. It dissolves with effer vescence in acids, and the nitro-muriatic acid extracts the gold from it.