Jet is generally classified as a lignite coal and has a high carbon content and a layered structure. It is typically black to dark brown and can sometimes contain tiny inclusions of pyrite. Jet has been carved for ornamental purposes since prehistoric times. The term “jet black” gets its name from the color of jet. There is hard jet that forms in saltwater and soft jet that forms in freshwater.
In 1996 a German company started marketing Japanese Freshwater Pearls as Kasumiga Pearls. The average size of these are between 10mm to 15mm but can grow up to 20mm. Kasumiga Pearls are known for their excellent color and luster. The most valuable pearls are round to near round but they also come in interesting baroque shapes.
Kornerupine comes in colors ranging from brown to beautiful emerald green to shades of yellow. It has distinctive trichroic pleochroism. Star material has been found in Mogok, Myanmar and is due to tiny rutile and graphite inclusions. Because of its extreme rarity, kornerupine is a highly sought-after collectors stone.
Kunzite is the pink to violetish purple variety of spodumene. The stone gets its color from trace amounts of manganese. Kunzite is better known than other spodumene varieties like hiddenite (green) and triphane (yellow). To obtain the best color and saturation in a stone it must be faceted with the table perpendicular to the length of the rough crystal. Kunzite often forms in large crystals that are highly sought after by mineral collectors. Kunzite displays strong fluorescence and phosphorescence that also makes it attractive fluorescent mineral collectors.
Kyanite is named for the Greek word for blue, kyanos. And what a blue! Fine Nepali kyanite can resemble the finest sapphire. Kyanite was a gem far better known to mineral collectors until more recent finds in the Kali Gandaki river region of west central Nepal, the first source to produce a significant amount of facet grade kyanite. Prior to the Nepal discoveries, Brazil was a major source of mineral specimen material, but kyanite also occurs in a variety of locations around the world. More recent kyanite discoveries have yielded additional colors, including orange and green.
Labradorite is a plagioclase feldspar. The phenomenal variety that shows labradorescence is the best-known variety, but rainbow moonstone, Oregon sunstone, and transparent yellow labradorite are also labradorite feldspars. Displaying brilliant pastels and deep golden colors, phenomenal labradorite features a spellbinding "black rainbow" of color. When appreciating the iridescent play of colors known as labradorescence, observe the strength and intensity by viewing from different angles, as different colors or even a range of colors may be visible from different positions. Rainbow moonstone has the best transparency of all the moonstone varieties. Labradorite sunstone is the only sunstone variety that contains copper platelets. The large sizes and clarity of yellow labradorite makes it a favorite of gemcutters.
Discover the mystical allure of rich, royal blue and sparkling golden specks found in lapis lazuli. Very few gems have such a long and storied history as lapis lazuli. Along with carnelian, it is the oldest known gemstones to be appreciated and worn as adornment. When lapis lazuli was first introduced to Europe, it was called ultramarine, meaning "beyond the sea." The gem was ground to a powder for use as early eye shadow, and as pigment for early oil paints. Today, this rich blue gem still retains the allure that first captivated humans thousands of years ago.
Larimar is a rare blue to green variety of pectolite, a mineral prized mainly by specimen collectors. While pectolite may be found in several locations, including Canada, England, and the U.S., larimar is found only in the Dominican Republic. This unique blue gem formed from volcanic activity millions of years ago that created the Caribbean island of Hispaniola. The most prized larimar exhibits sky blue color with a white pattern throughout, reminiscent of sunlight dancing on the floor of a pool. This gem was named by its discoverer for both his daughter, Larissa, and el mar, the sea.
Larvikite is a feldspar-rich igneous rock, called a monzonite and is named for the town in Norway where it was found. One characteristic of this stone is its blue sheen or labradorescence, caused by the presence of interlocking feldspar crystals within the structure of the stone. Through the wonders of nature, each polished gem has a sheen that sparkles with deep silver tones. Usually, this stone is used in ornamental and decorative purposes.
Also known as scoria, lava rock is formed from solidified volcanic lava. A defining feature of this rock is cavities caused by trapped gas bubbles. Unlike pumice, however, lava rock does not float on water. The unique look of this highly porous rock, along with its relatively light weight, makes it popular for jewelry and ornamental carvings.
This mineral species can be opaque to crystalline transparent. The color of lazulite ranges from medium to dark greenish blue to violet blue and is often mottled with white. When fashioned into gems, finished stones typically weigh less than 5 carats. A separate mineral species, lazulite should not be confused with lazurite or azurite.
Lazurite is a richly colored blue mineral primarily seen in cabochon gems or carvings. Lazurite is a major component of lapis lazuli, giving the stone its brilliant blue color. Lazurite crystals are rare, as the gem is most commonly found in massive form and rarely as well-formed crystals.
Lepidolite is a beautiful lithium-rich member of the mica mineral family. Violet to pink in color, lepidolite has a scaly appearance seen in many specimens. This gemstone is not commonly known to be faceted and is primarily used in ornamental and decorative pieces.
Liddicoatite is a calcium-rich lithium species of tourmaline named in 1977 in honor of noted gemologist Richard T. Liddicoat. Gems may form in green, pink, red, blue and purple colors, sometimes with internal multicolor banding and zoning. Large crystals are often sliced to display their natural multicolor designs.
Limestone is composed mainly of calcite and occurs in thick extensive, multiple layers. It is formed in shallow seas from a combination of calcium carbonate or the accumulation of shells and skeletons of calcareous marine organisms. Limestone is abundant and is very important commercially as it has a number of different uses as a building stone, cement and as a raw material in the glass manufacturing process. Limestone that is recrystallized under heat and pressure becomes marble.
Limonite gets its name from the Greek words for “marshy lake” because it is found in marshes. Limonite is a mineraloid that contains varied amounts of goethite and hematite, forming from weathering of hematite, magnetite, and pyrite. It is often found as a pseudomorph as it replaces other minerals.
The shell of the Pteria penguin, better known as the penguin's wing oyster, have a wing-like extension on one side of the shell is called “Mabé gai” in Japanese. The name “Mabé pearl” is inspired by this reference. The shells of the Pteria penguin and the Pinctada maxima are used to create blister pearls. The Haliotis variety of Abalone has also been used to create “Mabé pearls”. A plastic or wax half or three-quarter spherical or pear-shaped or heart-shaped nucleus is glued to the inside of shell. After two or three years of nacre growth the blister pearl is cut out of the shell. The nucleus is then removed and filled with resin and is backed with mother-of-pearl. The sizes range from 12mm to 25mm. They are more affordable than true cultured pearls.
The Madeira name comes from the Brazilian word meaning ‘wood’ or ‘wood colored’. Most madeira citrine comes from heating amethyst with a brownish core to get the warm yellow or orange color. The primary sources come from the Brazilian state of Rio Grande do Sul, Uruguay, Zambia, and Madagascar.
Magnesite, a member of the calcite mineral group, is often found in massive form, as well-formed transparent crystals are rare. Pure magnesite crystals are colorless, and any impurities present affect their color which is typically light yellow to brown or gray. Magnesite has perfect cleavage in three directions, making faceting extremely difficult. Faceted gems are often found in private collections or museums.
Malachite is generally opaque and comes in a vivid bluish green to green color. It is usually banded in two or more tones of green and may have a subtle sheen. This gem is a secondary copper mineral and is commonly found in conjunction with azurite, a bold blue copper carbonate mineral. A mix of the two minerals is often called azurmalachite.