Gold was popular with ancient civilizations for its brilliant shine. Because gold is a soft metal, it is easy to work with allowing early artists to manipulate it. Gold is also a rare element making it more expensive to mine.
Karat" tells you how pure the gold is. 24K gold is 99.999% pure gold. 18K is (18/24)=75% pure gold and 25% other metals. "Karat" refers to the purity of the gold. 24K (karat) gold is 99.999% pure gold. 18K is 18/24 or 75% gold and 25% other metals.
Which is better is a personal choice. 18K gold costs more because of its higher gold content. 18K gold has a higher gold content making it more yellow. The higher gold content also makes it softer. Jewelry made with 14K gold can hold stones a better because the 58.333% of other metals stiffens it.
All jewelry we sell is 14K white or yellow gold. Its karatage is also stated on the item description. If the karat stamp was on the portion of your jewelry that was removed for resizing, the karat stamp will be missing. Sometimes the jewelry manufacturers rush orders and skip the stamping process.
You can perform some tests yourself on the gold.
Looking at the gold, are there any black, silver or other color blotches in it?
When you hold the gold item, does it feel heavy?
Does it have a karat stamp on it?
The following table shows common locations for the karatage stamp.
On the inside surface of the ring.
On the post.
On the back. Sometimes on the chain loop
On the clasp.
Gold is the only yellow metal that does not react with nitric acid. Test kits using an acid are available at jewelry supply stores. The test usually involves rubbing a miniscule amount of the metal on the supplied paper and putting a drop of the acid on the paper rubbings. If the color does not change, it is real gold. 10K gold or less may react to this test due to the low gold content.
Another test you can use is the price test. If the price is too good to be true, it probably is. To figure out the value of the jewelry, you need to know the current market value for gold, the weight of the gold jewelry in ounces and its karatage. The value can be calculated as:
value = (gold market value) x (weight in ounces) x (karatage/24)
For example, if the price of gold is $900 per ounce, and you are looking at a 22K gold pendant that weighs 1/4 ounces, the formula would be:
Value=$900.00 x (1/4) x (22/24) = ?
Value=$900.00 x (25) x (91.667) = $206.25
The price can be higher for workmanship or branding, but if the asking price is $100, you can be sure that the pendant is not 22K gold or even real gold.
24K gold is yellow and yellow only. Gold can be mixed with other metals to create other colors. The following chart shows what combinations of other metals are used to create the different colors of gold.
Platinum is a relatively recent addition to the precious metals used in jewelry compared to gold. Platinum will not corrode, tarnish or rust. An added bonus to platinum jewelry is that the metal itself is very hard compared to gold or silver. Platinum is often mixed with iridium to further harden the metal making it stronger to hold precious stones, but harder to work with.
Platinum is a very rare metal... rarer than gold. Platinum is also heavier than gold. Jewelry made with platinum will weigh more than the same piece of jewelry made with gold. Due to its high melting point and cooling, it is also difficult to work with. Annually, 113 tons of platinum is mined compared to the 1782 tons of gold mined.