Gold: Gold is a type of Precious metal whose chemical symbol is AU 

Temperature: The melting temperature of Gold is slightly lower than that of copper at 1945 ° F or 1063 ° C ( Iron is 2802°F and Copper is 1981°F ) 

Specific Gravity: of gold is 19.32 Density: One cubic inch of pure gold weighs 10.18 troy ounces.

Weight: Gold for Jewelry purposes is weighed in Grams, Pennyweight (DWT) or Ounces (troy) 1 Troy ounce is equal to 31.10348 grams or 20 DWT (pennyweight) 1 DWT (pennyweight) is equal to 1.555 grams or 0.05 troy ounces. Karat: The most popular jewelry made in gold is 10 karat,14 karat, 18 karat and 22 karat gold Jewelry.

Purity: The purest form of Gold considered 24 karats is equal to roughly 99.9 percent purity 

Karat: When we say 24kt or 24k Gold jewelry, we mean that all the 24 parts in the gold are just pure gold without traces of any other metal(s) or 99.9 percent pure. When we say 22kt or 22k Gold Jewelry we mean that 22 parts of the jewelry, is gold and the balance 2 parts are some other metal(s) or equal to 91.3 percent gold plus 8.6 percent of some other metal alloy When we say 18Kt or 18k Gold Jewelry, we mean that 18 parts of the jewelry is gold and the balance 6 parts is some other metal or equal to about 75 percent gold plus 25 percent of some other metal alloy We can roughly state that each Karat is equal to approximately 4.1625 percent. The difference of the other metal or alloys of the metal, gives the jewelry its hardness and color. We can state that 24 Karat is the softest and 10 karat the hardest, because 10kt would have 41.6 percent gold and the balance would be other metals which are mostly harder than gold.. The color from the other metals enhances the beauty of the jewelry as the case may be, white gold, yellow gold, red gold etc. 

Density:  Gold has much higher density compared to other metals which are used as alloys, so the higher the purity of gold the heavier the weight of gold jewelry. For example a chain of same thickness will vary in weight if made in different karats of gold, it will be the lightest in 14kt and heaviest in 22kt gold, because 14kt has 58.3 percent gold compared to 22kt which has 91.6 percent gold.

22 karat gold : Being 91.3 percent in purity and hence very soft and malleable, very intricate designs of gold jewelry with beautiful intricate designs can be made in 22 karat gold. Although soft compared to other metals, the 22kt gold jewelry does not get easily damaged, and can be worn for years, and still maintain its luster and beauty. Note that most gold jewelry whatever the karat value does not get damaged by wearing, but rather gets damaged or broken by storing it improperly, jewelry when properly stored, in original boxes, and cleaned at regular intervals, will rarely break, damage or lose its luster and beauty.

Carat : Carat and Karat are not to be confused, Carat is not a percentage, it is rather a measure in which gemstones are weighed, the word carat was derived from the carat seeds which were once used for measuring as they were mostly constant in weight. 1 carat or ct. is equal to about 200 milligrams or about 1/5th of a Gram. For example a  huge 5 ct. pc of diamond would be just 1 gram in weight. (that is the reason why our precious and semiprecious stone gold jewelry is expensive compared to plain gold jewelry)

KDM: Gold Jewelry from some places is / was marked with a KDM stamp which means that the Jewelry was soldered with Cadmium. Cadmium called  'Kadium'  in some places and marked KDM was traditionally used in soldering of gold jewelry for its good properties of liquidity and melting at lower temperatures, which is not the case any more as Cadmium is known to create toxic fumes when melted, which are very dangerous to health, over a period of time and may be harmful to humans, making the gold jewelry, some countries have banned the use of Cadmium from use, from workshops. Jewelers in many parts of the world now use gold solders, which are free from Cadmium. Please note that the wearer of the gold jewelry is not harmed, this issue only concerns the manufacturing process. Also note that using any type of gold solder either KDM (Cadmium) or other gold solder, to make the jewelry does not guarantee the purity of gold, as the purity is a representation of the percentage of gold in any metal.

Gold Colors and finishes: Pure 24 karat gold is Yellow in color, when the purity is lowered, by adding different alloys, the color of the gold can be changed to reflect the color of the alloy. i.e. if we were to convert 24k gold to 22k gold we would be adding about 8.4% alloy, which would now make it 91.6 percent pure (22 karat). The addition of alloy has various purposes, one is to give it hardness, to make the gold jewelry stronger, as pure gold is very soft, the other would be to change the color, e.g. if copper would be added to alloy then the gold would appear reddish, instead of the yellow or if any of the white metal was added to the alloy it would make it appear white. This is not to be confused with the finishing, which are just on the top surface of the jewelry, which are mostly different types of hand paints or coatings, used like paint on the surface to enhance just the look, e.g. to give it an antique look, underneath the paint or coating, it would be solid yellow gold.