Gold
As coin for trade, decoration of courts and castles, or jewelry for adornment, gold has been use to symbolize wealth, status, and expressions of love for thousands of years.

Gold is found in igneous rocks and in associated quartz veins, often in small quantities invisible to the naked eye. It is also concentrated in secondary “placer” deposits as nuggets or grains in river sands and gravels. Gold bearing rocks occur in Africa, California and Alaska, Canada, the former USSR, South America and Australia.

Native gold is typically golden yellow, but in order to vary its color and increase its hardness for use in jewelry, gold may be alloyed with other metals. Gold can be alloyed with different metals to change its color from yellow to white, green and even rose.

24-karat gold is pure, 100% gold. 18-karat indicates that the gold is eighteen parts gold and the remaining six parts alloy making it 75% gold (18/24 = .75). Likewise, 14-karat gold is fourteen parts gold and the remaining ten parts alloy making it 58.3% gold (14/24 = .583). Given the preceding formula, what is the gold content of 10-karat gold? That’s right, 10/24 = .416 or 41.6%.

On the Mohs hardness scale gold is approximately 2.5