It has been a mooted question as to proper dividing line between stones that deserve title “precious,” and those, which should be placed in a so-called semi-precious or lower category. To draw such a line is hardly possible, as neither hardness, rareness, nor value would be a positive test--some of hard stones, like zircon and almandines being less valuable than softer opal, while diamond, one of most plentiful of precious stones, is at same time, one of most valuable.

Neither can price be taken as a complete test, because fashion makes a turquoise, an opal, or an emerald much more valuable at one time than at another, All precious minerals used for ornamental purposes, from diamond to quartz, or chalcedony, may properly be termed precious stones.

The Final Word On Precious Stones

The most precious stones are diamonds, emeralds, rubies and sapphires. The pearl is oftentimes classed with precious stones. Although strictly speaking while it is not a stone it holds an esteemed place in jewelry.

Pure silver has a beautiful white color and luster; it is almost as plastic as pure gold and like it very soft. Silver does not tarnish in natural air, but when it comes in contact with sulfur compounds it readily forms black silver sulfide. The sulfur compounds which act on silver are found in small quantities in air as a result of burning coal and illuminating gas, while larger amounts occur in vulcanized rubber, wool, and foods like eggs.

Pure silver is too soft to make durable objects that require lightness and stability of form. This defect is overcome by alloying it with a little copper.

An alloy of 925 parts fine silver and 75 parts copper is called 925-1000 fine or what is commonly known as sterling silver. This alloy is used almost universally for jewelry and best silverware.