The pearl is usually measured by the grain; a grain equals ¼ of a carat, or one twentieth of a gram (0.05 gr.). (This grain is not to be confused with the grain that is the smallest unit in the English system of weight.) Any pearl which is less than one quarter of a grain is called a seed pearl; an ounce of these may contain as many as 7,000 to 9,000 pearls. They are used in embroidery, in weaving cloth, and for many-stranded chains. _The Precious Metals_ The purity of gold is also measured in carats; in the United States, to distinguish the two systems, the gold weight is spelled with a _k_: karat. Pure gold is spoken of, arbitrarily, as being 24 karat gold. Pure gold, however, is too soft for most uses, especially in jewelry; it is therefore mixed with a harder metal; the mixture, and the less valuable metal used in the mixture, are both called the alloy. The number of karats of gold indicated is the proportion of pure gold in the alloy. Thus, 18 karat gold means 18 parts of pure gold mixed with 6 parts of alloy. _Alloys_ The alloy is usually formed by fusing metals together; when molten they dissolve in each other and form an intimate union, often (as in industrial uses) producing a new metal with qualities quite different from those of the separate elements of the mixture. The admixture of nickel or zinc with gold produces what is called white gold; an alloy of copper or brass is red gold, ranging in color from pink to deep rose; an alloy of silver is green gold. In addition to gold—mainly 20, 18, and 14 karat gold—pure (sterling) silver, platinum and, more recently, palladium are also effectively employed for jewels, alone or as background in which to set precious stones. Other precious metals occasionally used in the making of jewels are iridium, rhodium and ruthenium. The favorites, however, continue to be platinum and gold. CHAPTER 14 _The Care of Jewels_ _How to Care For Jewels_ There are many misconceptions as to the care and the cleaning of jewels. And there is but one sound rule. When jewelry needs to be cleaned, take it to the jeweler. A woman who takes her jewels to a jeweler, to have him clean them, is showing that she regards him as her regular dealer; as such, he will be happy to clean them without charge. At the same time, he will check the settings, the clasps, the safety catches. While home cleaning might damage a stone, or loosen it in its setting, professional work restores the jewel so that it is both cleaner and more secure than before. _Home Care_ There is one way in which a woman can help to keep her jewelry clean. Every time that a jewel is worn, it should be wiped with clean tissue paper, or chamois leather, before being put away. (Facial tissue should not be used, as it will leave a fuzz.) Such a gentle wiping will remove the grease of finger-marks, and other marks or specks. _Cleaning Don’ts_