Beijing is a metropolis in northern China and the capital of the People's Republic of China. It is one of the four municipalities of the PRC, which are equivalent to provinces in China's administrative structure. Beijing is one of the Four Great Ancient Capitals of China. The municipality of Beijing borders Hebei Province to the north, west, south, and for a small section in the east, and Tianjin Municipality to the southeast. Beijing is China's second largest city, after Shanghai. Beijing is a major transportation hub, with dozens of railways, roads and motorways passing through the city. It is also the focal point of many international flights to China. Beijing is recognised as the political, educational, and cultural center of the People's Republic of China, while Shanghai and Hong Kong predominate in economic fields. The city hosted the 2008 Olympic Games.

Gold Jewelry

Because of the softness of pure (24k) gold, usually alloyed with base metals for use in jewelry, altering its hardness and ductility, melting point, color and other properties. Alloys with lower caratage, typically 22k, 18k, 14k or 10k, contain higher percentages of copper, or other base metals or silver or palladium in the alloy. Copper is the most commonly used base metal, yielding a redder color. Eighteen-carat gold containing 25% copper is in antique and Russian jeweler. It has a distinct, though not dominant, copper cast, creating rose gold. Fourteen-carat gold-copper alloy is nearly identical in color to certain bronze alloys, and both used to produce police and other badges. Blue gold can be made by alloying with iron and purple gold can be made by alloying with aluminum, although rarely done except in specialize jewelry. Blue gold is more brittle and therefore more difficult to work with when making jewelry. Fourteen and eighteen carat gold alloys with silver alone appear greenish-yellow and referred to as green gold. White gold alloys made with palladium or nickel. White 18 carat gold containing 17.3% nickel, 5.5% zinc and 2.2% copper is silver in appearance. Nickel is toxic, however, and its release from nickel white gold controlled by legislation in Europe. Alternative white gold alloys are available based on palladium, silver and other white metals (World Gold Council), but the palladium alloys are more expensive than those using nickel. High-carat white gold alloys are far more resistant to corrosion than are either pure silver or sterling silver. The Japanese craft of Mokume-gane exploits the color contrasts between laminated colored gold alloys to produce decorative wood-grain effects.