How do you identify pure gold by naked eye?

The purity of items made from gold (jewelry, coins, or other memorabilia) cannot be identified visually except by markings such as 9k,10k, 14k, 16k, 18k, 21K, 22K, 24K or in number form such as 375, 416, 585, 750, 916 or 1000. In most Japanese jewelry, K18 is the usual hallmark for 18K. Chinese gold often has an ORIG hallmark which may be a company logo.

Every gold item whether it be Spanish, Italian, Singapore, Chinese, Japanese, or from the Middle East can be identifiable by the generic locks that comes with it. The S lock is seen on many Chinese gold chains. Lobster clasps can often be seen in Spanish and Italian gold with differences in terms of its shape. the newer Italian lobster locks are often pear shaped. The older spring locks can be seen in most vintage and antique gold jewelry. The clasp varies on thicker bracelets. Most Italians and Spanish have fancy locks while the rest use a double click push lock with a safety latch at the side.

Upon visual inspection, Spanish and Italian gold can be identified by its design. They often are more "fancy" with added color hues i.e. tri-color (rose gold, white gold & yellow gold). on a solid yellow gold. However, Spanish/Italian gold has a lighter yellow hue compared to most 18K or 14k with intricate artistic and fancy modern art (greek keys, elephants, medusa head etc) and due to this, most Italian and Spanish gold objects are plated or hollow, as solid gold would be very costly. Japanese gold is a more rustic brownish yellow color since their standard is K18 for 18K gold. Chinese gold is more "yellow," specially as it ages. Singapore and Middle East gold is often distinguishable by their cultural design; Saudi with more Arabic designs or symbols than Singapore. Singapore often has "diamond cut" designs to make them "sparkle," as does some saudi gold. Many Asian gold designs are also often solid and not hollow.

The higher the number, the purer (and softer) the gold. For typical hard wear applications like rings, you would not want gold purer than 18k.