Various characteristics of diamonds are graded and categorized by the diamond industry. Learning about diamonds is first learning about the "four Cs" of diamonds which are considered the most important grades and categories:
These are the criteria jewelers use when grading diamonds, and they're the ones you'll need to understand to buy the right diamond for you.
And then there's the "Fifth C": Certificates
The diamond certificate, which is sometimes called a grading report, is a complete evaluation of your diamond that has been performed by a qualified professional with the help of special gemological instruments. Each stone bears its own recognizable, individual characteristics, which is listed on the certificate.
Pure gold is a very soft and pliable metal. The extreme malleability, ductility, and softness of pure gold makes it practically useless for jewelry applications. Jewelry made of pure gold would easily bend and distort in the course of normal wear. To get around this problem, jewelers use an alloyed form known as karat gold (not to be mistaken with metric carat used to measure diamond weight). Alloying increases gold's hardness and provides a variety of different colors. White gold contains about 10 - 20 % nickel, plus zinc, copper, platinum, and palladium. These alloys make white gold a harder metal than yellow gold. Gold content is specified by the karats 14k, 18k, etc. The K (karat) number specifies how many parts, by weight, of pure gold is contained in 24 parts of the alloy. And of course, 24k means 100% pure (or fine) gold. Gold itself is impervious to tarnishing and requires very strong and dangerous chemicals for it to dissolve.
Platinum is regarded as the preeminent metal for fine jewelry. It is rarer and thus more expensive than gold. It is also the strongest precious metal used in jewelry, and is almost twice as heavy as 14k gold. This weight is one of platinum's strongest selling points, because it gives "bulk" to fine jewelry, which people naturally equate with value. Platinum has rapidly grown in popularity in recent years, becoming the new choice for many diamond engagement rings because the luster of platinum is said to bring out the brilliance of diamonds better than gold. Platinum in jewelry is actually an alloyed group of six heavy metals, including platinum, palladium, rhodium, ruthenium, iridium and osmium. Today it is often alloyed with copper and titanium. It is the only precious metal used in fine jewelry that is 90% to 95% pure, largely does not cause an allergic reaction and tarnish-resistant. Platinum jewelry is marked 900Pt, 950 Plat, or Plat.