CURIOUS FACTS ABOUT MINERALS.

Oamaru Mail, Volume XXXVIII, Issue 10502, 9 July 1910, Page 3 (Supplement)

CURIOUS FACTS ABOUT MINERALS.

(By Sir Ray Lankester, K.C.8., F.R.S.) ■'One of the most-curious and valuable minerals formed by aluminum is lapis laziilli, found in Central Asia, Persia, and China, used for ornamental "inlaying," and also, when powdered, used as a paint, which is called "ultramarine." It is a very curious fact that,, though the'compounds of aluminum are, when pure, colorless —even "white sapphires" being known and the color of the ruby and the blue sapphire being due to the admixture of minute traces-of colored oxides of other metals—yet the fine blue color of ultramarine is not due to any such admixture. Ultramarine consists only of silica, aluminum and sodium, with a considerable quantity of imeombined sulphur. It used to be of enormous value when obtained onlj T as a mineral, but it is now prcjjared artificially on a large scale by heating a mixture of these elements in a crucible. It is used as a paint (about 10,000 tons a year), and whereas the natural ultramarine was worth its weight in gold, the same compound, prepared artifically, is now sold for £1 lis 3d per hundredweight. Its exact nature is still a puzzle to the chemists. It has been suggested, and is not improbable, that it owes its blue color to very fine particles of sul-

plmr disseminated throughout the translucent combination of silica, aluminum and sodium (a sort of glass), the particles acting on light in the same way as uo the fine particles in blue smoke, and as do the fine particles in the skin of a blue frog of the Riviera, and in blue eyes of men and women. Tin was known even to prehistoric, man which was of a fibrous strucratm. It was called "plumbun candiJnm" and also "stannum" by the Romans, and "cassiteron" by the Greeks. By the alchemists it was spoken of as "the devil of metals," because it forms brittle alloys with other metals. 'The Phoenicians brought tin from the tin islands —called the Cassiterides—which are now supposed to have been Cornwall. It was carried in carts

across Mount's Bay to St. Michael's Mount in Roman times, and was then conveyed through Gaul to Marseilles, and so to Italy. But it has been found abundantly in the Malay peninsula and neighboring islands. It only occurs with extreme rarity in the pure elemental state, and its commonest ore is the oxide or "rust" known as tin-stone. It is probable that although the Mediterranean peoples fetched tin-stone in early times from Britain, yet still earlier Eastern races — . who made "bronze" implements —obtained it from the Malay region. A tin was known even to prehistoric ture, and when bent emitted a peculiar crackling sound. At a low temperature, such as one may get in the severest winters, tin breaks up into a gray powder, and this curious fact was known to Aristotle. Tin is used not only as "tin foil" and to make vessels for household use, but also for covering or "tinning" copper and iron '(tin plate). Tinned copper vessels were made, by the Romans, and are described by Pliny. Tin is, however, chiefly used in producing alloys. "Bronze" is the name given to any alloy consisting oliiefly of copper and tin. "Gun metal" is a yellow bronze: "bell metal" is another. The addition of phosphorus and in other eases of arsenic to the alloy gives special and valuable properties. Pewter is the alloy of tin and lead, harder and' tougher, but more readily fusible than cither ol its constituents. Lead had been used before this to coat glass, so as to form a mirror, whilst earlier mirrors were made <>t polished metal. Lead is mentioned n the Book of Job, and is one of the seven ancient metals, associated by archaeologists with the seven planets known in early times and with the seven days of the week. These ancient metals, the only ones known in early Rome and Greece, are gold, copper, tin, lead, iron and mercury. Lead occurs rarely in the free state in Nature. Its commonest ore is its coiitpoutul with sulphur, c:illcd_ "galena," in which silver'is often associated with it.. Galena commonly occurs in the form of cubic crystals. Tlisy pure lead is easily extracted by, melting the ore, mixed with charcoal, in a furnace, when it runs out in a molten condition from the

bottom. . Pure lead is a soft metal, and can easily be rolled out into thin plate or foil, but cannot be drawn in a wire of any length, though lead-tubing is produced by forcing' lead by great pressure through a ring-like opening. Small quantities of other metals mixed with it render lead brittle, and it lias, when molten, a disastrous effect upon plate or foil of other metals, such as gold, silver, and platinum, fusing them into alloys, perforating, and, as it were, corroding them. In connection with the manufacture of white lead, which is carbonate of lead, greatly used as a paint and protective coating—"red lead" is an "oxide," or rust of lead —and in the use of drinking water which has passed through leaden pipes, as well as iu the use of lead compounds to give a glaze to pottery, and even in the handling of lead piping and sheeting, lead has acquired ail evil reputation, since it often causes serious poisoning of a very peculiar kind. It slowly accumulates in the system, causing "first painter's colic, then leadpalsy, epileptic fits, and often total paralysis. Lead poisoning is_ recognised by a blue line at the edge of the gums due to the deposition of lead sulphide.

Ordinary potable water does not dissolve lead, but distilled water, or water which is very pure, but contains ammonium nitrate, or excess of carbolic acid —under pressure —takes up lead from a cistern or pipe, and causes lead poisoning to those who habitually drinit -Yntimonv, also called Stibium, is nearly being one of the great metals of antiquity, for its sulphide was well known and used to give.a black pencilling to the eyebrows by the ancients, as well as in metallurgical processes. This substance was actually called kohl, or al-koliol, by the Arabs, that word beinrr applied to a "powder, and only "A later usage to distilled spirit, and it is still used in the East, and known by that name. „ . , Antimony is a very remarkable body, allied 111 many of its properties to the quasi-metal, arsenic, and so -to piios-

pliorus. It is prepared in dark crystalline masses, looking like nmiiature fortifications and battlements. It is used lamely as an alloy, giving fusibility and other valuable qualities to the metals frith which it is mixed, .but .it is perhaps best known m medicine, its combination .with tartaric acid being the once familiar "tartar emetic, -bismuth, also called "mareasite, is a comparatively rare metal, occasionally found pure, but chiefly obtained nom 01 Its "rust" is used in the form of a white powder as a cosmetic, and the metal itself for the manufacture pt alloys of low melting point. It is remarkable for the fact that it expands when passing from the molten to the solid condition, thus resembling water; whereas other metals contract on solidiflCChromium is not found in the free state, but is fairly abundant as chrome-iron-stone. It resembles iron, and is used to form alloys with iron of great hardnSss. It is remarkable as one of the great "color-producing metals, some of its combinations being green and others yellow and orange. The emerald owes its line green color to the presence in it of small quantities of chromium. "Chromates are largely used as pigments, and in photographic printing processes, in connection wrtn j "-elatine. Molybdenum is a rare metal, once confused with graphite, or plumbago. It is used, as an alloy, to mate

certain kinds of steel. . A most valuable tm alloy is the "amalgam" wliicli mercury forms with tin. It is of a creamy consistency, ami is the basis of ail important indiistrj, the manufacture of looking-glasses. A Sheet of tinfoil is placed on a perfectly smooth slate table and mercury is spread in a, thin am over it Then a carefully cleaned sheet of plate-glass is floated 011 to its surface, and weights placed on the glass, so as to squeeze out the excess of mercury. The amalgam' adheres to the glass as a thin coat. This process was first described at the

end of the seventeenth century. Tungsten is found in a mineral called wolframite, abundant in Cornwall, Cumberland, and other places. One of its soluble compounds lias been largely rsed to render muslin uninflammable. The metal itself has lately been introduced as a filament for incandescent lamps.