Gold spiked to a 23-year high and silver rose to its highest for 18 years on Friday in a volatile bull market driven by fund managers, who are seen pushing the market further higher, dealers said..Gold, used as jewelry and investment, has been on the rise as investors diversify their portfolios on worries about economic growth and inflation. Gold rose to as high as $506.50 an ounce, its highest level since February 1983, and looked likely to rise further as fund buying resurfaced despite fears of year-end liquidation. "There is a lot of money that just buys it because there is an uptrend," said Robin Edwards, president of UK-based Saber Fund Management. "The investment money sees an environment where gold is an interesting alternative investment. Diversification is the key these days. The fundamentals are very good on gold." Spot gold (XAU=) was quoted at $504.70/505.50 an ounce by 1105 GMT, up slightly from $503.00/503.75 last quoted in New York on Thursday. Some dealers expected gold to trade in a wide range of between $490 and $510 for the rest of the day. Gold climbed to $509.20 an ounce in February 1983. Anything above that level will bring the metal to its highest since January 1980, when it hit a record high of $850 an ounce. "Certainly commodities seem to be the flavor of the month at the moment and the funds have continued to buy," said Simon Weeks, director of precious metals at ScotiaMocatta.