Natural alloys

When you see Dr. Wollaston give him a thousand compliments from me and then ask him if it would be possible to have a little malleable platinum, not separated from its natural alloy with palladium, rhodium, etc, to make a crucible. The crucibles I have bought recently from Cary are of a metal noticeably purer than those which I formerly had, and for that very reason infinitely more susceptible to attack by other substances (5). 

It is not improbable that the ancient metallurgists by their somewhat crude methods, succeeded in removing silver from its natural alloys with gold, at least to the extent... 

Native elements are minerals composed of a single element. This group also includes natural alloys, which are mixtures of two metals. Based on their physical properties, the native elements can be separated into three divisions metals (such as Ag, Au, Cu, Fe, Hg, Pb, Pt, Sn), semi-metals (such as As, Bi, Sb, Te), and non-metals (C, S, Se). 

Most native gold is actually a natural alloy of gold with a small amounts of silver (10-12%). Electrum is an natural alloy of gold that contains 20% or more silver, written Au, Ag. 

An alloy is a mixture of two or more metals, or of a metal and a non-metal. Many minerals are natural alloys, being compounds of metals or a metal/ non-metal combination. Most of these fall into the native element, sulfide and sulfosalt mineral groups. 

The processes involved in the reduction of nickel ores vary considerably, both with the chemical composition of the ore employed and the nature of the product required. For example, the Sudbury (Ontario) ores consist essentially of sulphides of nickel, copper, and iron. When pure nickel is required it is, of course, essential to remove the copper and the iron. Sometimes, however, an alloy of nickel and copper, known as monel metal, is desired, and it is usual then to remove the iron and subsequently reduce the mixed sulphides of copper and nickel to the alloy direct. Monel metal is thus known as a natural alloy, inasmuch as the constituent elements have not been individually isolated. 

A very important alloy containing 25 per cent, of nickel and 75 per cent, of copper finds extensive application in the manufacture of currency both in Europe and in the New World. Reference has already been made to this in previous pages.1 Monel metal is an alloy of nickel and copper made by the Orford Copper Company by direct reduction of the nickel-copper matte obtained from the Sudbury ores (see p. 82). It is therefore termed a natural alloy. It contains from 60-72 per cent, of nickel, the remainder consisting mainly of copper with iron ranging from 0-5 to 6-5 per cent. The United States Government specification, issued in July 1910, for monel metal requires 8... 

Occurrence and History.—Osmium occurs in nature alloyed with iridium as iridosmine or osmiridium, which is found as irregular flattened grains and, more rarely, as hexagonal prisms. It has a metallic lustre, tin-white to light steel-grey in appearance hardness 6-7 density 19-3 to 21-12.1 It occurs in Choco, South America in the Urals in auriferous and other drifts in New South Wales in auriferous beach-sands of North California and also in gold washings of certain Canadian rivers.1... 

Occurrence and History.—Iridium is found in nature alloyed with platinum or other allied metals, particularly in platiniridium and osmiridium (see analyses, pp. 208, 258). Nevyanskite, a variety of osmiridium, contains over 40 per cent, of iridium, whilst siserskite, another variety, contains up to 80 per cent, of the same metal.1... 

Derivation Occurs with platinum, from which it is recovered during the purification process. Also occurs with iridium as a natural alloy, iridosmine. 

Occurrence in earth s crust about 0.001 ppm. Discovered in 1804 by Tennant. Occurs in nature in the metallic state, usually as a natural alloy with osmium (osmiridium) found in small quantities alloyed with native platinum (platinum mineral) or with native gold. Recovery and purification from osmiridium Deville, De-bray, Ann, Chim. phys. 61, 84 (1861) from the platinum mineral Wichers, J. Res. Nat. Bur. Stand. 10, 819 (1933). Reviews of prepn, properties and chemistry of iridium and other platinum metals Gilchrist, Chem. Rev. 32, 277-372 (1943) W p. Griffith, The Chemistry of the Rare Platinum Metals (John Wiley, New York, 1967) pp 1-41, 227-312 Livingstone in Comprehensive Inorganic Chemistry vol. 3, J. C. Bailar Jr. et at, Eds. (Pergamoti Press, Oxford, 1973) pp 1163-1189, 1254-1274. 

Bronze age implements have been found in Hungary containing copper alloyed with antimony up to 4 to 5 per cent. Like the Egyptian arsenical copper already mentioned, this was purely a natural alloy. Undoubtedly metallic antimony was known in very early times. A vase, found by de Saizec at Tells in Chaldea, was analysed by Berthelot in 1887, who found it to consist of almost pure antimony, whilst a copper ewer and basin dating from the Fifth or Sixth Egyptian Dynasty have been shown to be coated with antimony (p. 93). Ancient beads of fairly pure antimony were found by Petrie in a tomb at Illahun dating back some 800 b.c. 

The notorious black powder was, evidently, a natural alloy of osmium with iridium, the so-called osmiridium. Iridium is known to be chemically stable and in the compact form does not dissolve even in aqua regia. On the contrary, osmium is readily soluble in aqua regia in general among platinum metals osmium has the most atypical chemical... 

Buffon still thought that platinum was a natural alloy of gold and silver containing iron, and Richter (see p. 675) used the symbol )0 for it. The name platinum is used by J. L. Fournier. Thomson says the name platina was changed to platinum by Linnaeus, this name being adopted by Bergman,... 

---