When spelled with a "c," the word "carat" refers to the units used to measure the weight of jewelry stones. When spelled with a "k," the word "karat" is a qualitative designation used to describe the fineness of a metal. Every jewelry metal is an alloy which contains different metals in various amounts. Pure gold, for example, is much too soft to be used for jewelry. For this reason, gold (and certain other precious metals) are typically blended with other metals. The number of carats indicates how much of the precious metal is in the alloy. For example, the phrase "14 karat gold" means that 14 units of pure gold are contained within every 24 units of the alloy;

Random chance plays a role in the cultivation of pearls. Sometimes the oyster ejects the kernel that's been inserted into it to stimulate pearl production, while simultaneously keeping within its shell the piece of tissue that produces mother-of-pearl. When this occurs, an irregularly shaped pearl (known as a "keshi pearl") is formed. The smallest such pearls are no larger than a pinhead, whence the name "keshi," which is the Japanese word for "poppy-seed." Some keshi pearls, however, can grow as large as 10 mm in diameter. Keshi pearls occur in all species of bivalves that are used for pearl cultivation.

The Kimberley Mine was once an extremely productive diamond mine in South Africa. Diamonds were mined by the open-pit method there between 1871 and 1908. Without the use of machinery, workmen at this mine dug the largest hole ever excavated by human hands. Appropriately named the "Big Hole," it measures 460 meters in diameter and its shaft is 1,070 meters deep. Today, however, the lower half of the shaft is filled with water. Diamonds weighing a total of 14.5 million carats (nearly three tons) were mined there. The mine was abandoned in 1914 after a brief period of below-ground mining.

The name "Koh-i-Noor" means "Mountain of Light" in Persian and suggests what an extraordinary stone this famous diamond truly is. Like the equally legendary Hope Diamond, the Koh-i-noor traces its provenance to the mines of India. The Koh-i-Noor was first mentioned in 1304, when it had a round shape and allegedly weighed 108 carats. Other sources claim that it in fact weighed 186 carats. The gem came into the hands of the Persian conqueror Nadir Shah in 1739. After the country came under British rule, Queen Victoria received the gem in 1850. Reshaped into its present oval form, the diamond now weighs more than 105 carats. It has been set into the crown of the Queen of England and is kept in the Tower of London.

Kunzite, a variety of spodumene, occurs in pale pink and in shades of violet ranging from pale to dark purple with a pinkish veil. Kunzite has a lively, vitreous gleam. This attractive mineral is relatively delicate. Kunzite is extremely fissile. Brazil leads the world as the chief supplier of kunzite.