Gold was among the first metals to be mined and has been used for jewellery, embellishment and currency for thousands of years. Gold in its natural form is soft and yellow in colour. Pure gold is called 24 carat, while gold that is 75 per cent gold is 18 carat, 50 per cent gold is 12 carat and 42 per cent gold is 10 carat. Material with less than 10 carat gold is not considered to be gold in the United States. There are several ways to test items for gold without using acid or other chemical tests.
Scratch the gold item against a piece of glass. If the metal scratches, it is not pure gold and any gold content is low. Always use a section of the gold item that is less noticeable in case it scratches or leaves a mark.
Hold a magnet near the gold item. If the magnet is attracted to the item, there are other metals included in the material. Gold itself is very soft and non-magnetic.
Take a piece of unglazed porcelain and rub the gold item against it. If it leaves a black streak, the material is not gold. If it leaves a golden yellow streak, the item is gold.
Use a magnifying glass and examine the item closely. Most commercially produced jewellery in the United States will be marked with the gold purity, such as 24 carat (24K), 18 carat, 14 carat, 12 carat or 10 carat gold. The mark may be very small, hence the need for a magnifying glass.
Take the jewellery to an authorised jeweller for assistance in determining the purity of gold without using acid or other chemical tests.