Agate is a semipellucid crystallized quartz, consisting of banded or with branching inclusions chalcedony. Physical properties of agate are in general those of quartz. Agate has irregular, sometimes circular bands of color and often replaces fossil wood. Many fossils are agatized material where the original organic substance has been replaced by agate while retaining the original structure. Agates are identical in chemical structure to jasper, flint, chert, bloodstone, and tiger-eye, and are often found in association with opal. The colorful, banded rocks are used as a semiprecious gemstone and for making mortars and pestles. One will often see these in beads, agate pendants and necklaces. Agate comes in most colors. Agates range from transparent to opaque in a variety of beautiful colors. It presents various tints in the same specimen.
Aquamarine is pale greenish blue or bluish green variety of beryl. Beryl is a mineral composed of beryllium aluminum silicate, a commercial source of beryllium. It has long been of interest because several varieties are valued as gemstones. These are aquamarine, emerald and heliodor. Aquamarine is the most common variety of gem beryl, it occurs in pegmatite, in which it forms much larger and clearer crystals than emerald.
Amethyst is the most valuable transparent, coarse-grained variety of the silica mineral quartz that is valued as a semiprecious gem for its violet color. It contains more iron oxide than any other variety of quartz, and experts believe that its color arises from its iron content. Other theories attribute the color to contained manganese or hydrocarbons.Found in abundance, in its purest form, Amethyst is colorless. The finest quality Amethyst is medium to medium dark in tone, vivid in intensity, and purple, reddish purple to bluish purple in hue. Heating removes the color from amethyst or changes it to the yellow of citrine. Most commercial citrine is made in this manner.
Black Onyx The layers in these stones range from translucent to opaque for sardonyx. The stones vary in color, too. They may be white or gray, ranging to many colorful varieties. Sardonyx stones usually contain flat-banded, white and brownish-red bands. Onyx is a gemstone with alternating light and dark bands, which are colored in brown, red, black, white and grey.
Citrine is transparent, coarse-grained variety of the silica mineral quartz. Citrine is a semiprecious gem that is valued for its yellow to brownish color and its resemblance to the rarer topaz. Natural citrine is rare compared to amethyst or smoky quartz, both of which are often heated to turn their natural color into that of citrine. Pale yellow to a madeira orange in all of its glorious golden and yellow colors. The yellow color is from the presence of iron, the darker the color – the higher the grade.
Cubic zirconia (CZ), a replacement for diamond was first used for the production of jewelry stones in 1976. On the hardness scale for stones, the genuine diamond is a 10 compared to a hardness ranging from 8.5-9 for CZ. CZ has a refractive index (the ability to refract a ray of light into colors of red, orange, green, yellow, violet, and blue) of 2.15-2.18, compared to 2.42 for genuine diamond.
Diamond pave and micro pave settings, sometimes also called bead settings are made by fitting diamonds into tapered holes in the metal. Pave settings use numerous small diamonds put together in a cluster with little or no metal showing. The stones are set almost level with the surface on the ring and some of the surrounding metal is raised to form beads which secure the stones. The name of the style come from French word pavé meaning paved like a cobblestone road. In order to give the impression of a continuous diamond surface.
Diamond baguette The cut of a baguette diamond gets its name from the shape of the cut. A baguette cut is rectangular, long and skinny. The cut was named for the similarly shaped baguette bread loaf.
Gold Pure gold is so soft it is rarely used in jewelry. Jewelers deal with various gold alloys, collectively called karat gold. Karat (K) tells the number of parts, by weight, of gold in 24 parts of alloy. The higher the percentage of pure gold, the higher the karat. Pure gold is 24K. 18K is 18 parts fine gold and 6 parts metal; 14K is 14 parts fine gold and 10 parts metal; and 10K is 10 parts fine gold and 14 parts other metal.
Hematite is an iron oxide and is gray, red or black in color. It has a crystalline structure and is one of the most abundant ores of iron. It is the birthstone of people born in the month of March. The word hematite is derived from the Greek word “haimatites” which can be translated as blood like. Hematite stone has a very shiny surface and it has a luster similar to that of a precious metal.
Lapis lazuli is a semiprecious stone valued for its deep blue color. The source of the pigment ultramarine, Lapis lazuli is not a mineral but a rock colored by lazurite. In addition to the sodalite minerals in lapis lazuli, small amounts of white calcite and of pyrite crystals are usually present. Because lapis is a rock of varying composition, its physical properties are variable.
Morganite, also known as Pink Beryl, Rose Beryl, Pink Emerald and Cesian Beryl, is a light pink to salmon-pink gem quality beryl. Morganite was first recognized as a distinct variety when specimens were first discovered in southern California in 1911. The pink beryl was named after J.P. Morgan, the American financier and gemstone collector.Gem-quality beryl coloured pink or rose-lilac by the presence of cesium. It is often found with peach, orange, or pinkish yellow beryl (also called morganite); these colours transform to pink or purplish upon high-temperature heat treatment. Morganite crystals often show colour banding: blue near the base, through nearly colourless in the centre, to peach or pink at the terminations. This colour change is probably caused by differences in the composition of the solution from which the crystal grew. Morganite is commonly found as squat, tabular crystals in lithia pegmatites, as in southern California and New England.
Quartz is the second-most-abundant mineral in the Earth’s continental crust, after feldspar. There are many different varieties of quartz, several of which are semi-precious gemstones. Throughout the world, varieties of quartz have been since antiquity the most commonly used minerals in the making of jewelry and hardstone carvings.
Rose quartz is a type of quartz which exhibits a pale pink to rose red hue. The color is usually considered as due to trace amounts of titanium, iron, or manganese.
Smoky quartz is a gray, translucent version of quartz. It ranges in clarity from almost complete transparency to a brownish-gray crystal that is almost opaque.
Sterling silver is an alloy of silver containing 92.5% by mass of silver and 7.5% by mass of other metals, usually copper. The sterling silver standard has a minimum millesimal fineness of 925.
Tiger eye is quartz that contains oriented fibres of crocidolite that have been replaced by silica. Tiger eye is displaying chatoyancy (a vertical luminescent band like that of a cat’s eye). Tiger eye typically has lustrous alternating yellow or brown bands. Tiger eye has a rich yellow and golden brown stripes, with a fine golden lustre when polished.
Topaz is an aluminum fluorite silicate containing fluorine. It is one of the few gem minerals which, under suitable conditions, grow into enormous crystals. Topaz typically occurs in cavities in rhyolites and granite, in pegmatite dikes, and in high-temperature veins with cassiterite and tourmaline. The stone is transparent with a vitreous luster. A light yellow, brown and pink variety of topaz are valued as a gemstone. The pure crystals of topaz used a great deal in jewelry.
Tourmaline is borosilicate mineral of complex and variable composition. Tourmaline is very abundant and has the best-developed crystals in pegmatites and in metamorphosed limestones in contact with granitic magmas. The colored varieties, when transparent and free from flaws, are cut as gems. Transparent crystals of tourmaline are dichroic – the depth of color varies as the crystal is turned in the light. Another peculiarity of tourmaline is that crystal when heated acquires an electric charge and attracts small objects such as hair or small pieces of paper. Rubbing crystal imparts a similar charge. Tourmaline comes in many colors such as blue, yellow, pink, red, black, green and clear. Green is from iron, chromium and vanadium, pink from manganese. Some crystals are pink at one end and green at the other.