Cut: Refers to the geometric shape and proportions of a gemstone. A gemstone’s cut is what most directly affects its sparkle or brilliance.

Facet: A flat cut on the surface of a gemstone.

Fire: Flashes of rainbow colors. Also called “dispersion.”

Hardness: Resistance to scratching. The higher the number, the more resistant.

Hue: Another word for color.

Luster: The shininess of a jewel.

Opaque: The opposite of transparent. Light cannot pass through an opaque gemstone, therefore they do not have any sparkle or fire.

Saturation: This term refers to how pure or deep a gemstone’s color is. Some gemstones, like aquamarine, have a naturally low saturation (very light blue) while other gemstones, like amethysts, can have very high saturation (rich, dark purple).

Sparkle: The white light leaving a jewel, traveling upward, which is visible to the eye. Sparkle is often referred to as “brilliance.”

Toughness: Resistance to breakage.

Gemstone Shapes & Cuts
These are the common shapes or cuts for gemstones, each lending a different look and allure.

Baguette: Baguette means “stick” or “rod” in French, which makes it a very appropriate name for this gemstone shape. Diamond baguettes are often used as accent stones to flank a primary stone.

Brilliant: Any gemstone cut with 58 facets, which produces the maximum possible sparkle. A brilliant cut can have several shapes, including round, oval, pear, radiant and heart.

Cabochon: This shape features a rounded, perfectly smooth surface instead of facets. It is the oldest gemstone shape and is commonly used with opaque stones such as opal, jade and turquoise.

Cushion: A very popular style for most of the 19th century, cushion shapes are slightly domed with rounded corners that make the stone look like a pillow. In fact, this shape is often referred to as a “pillow cut.” It looks particularly beautiful in candlelight.

Emerald: With its long, steep facets, emerald cuts tend to flash rather than sparkle.

Fancy: Technically, this term refers to any type of gemstone that isn’t round, but many jewelers reserve it to describe the more exotic gemstone shapes such as marquise, heart, pear and trillion.

Heart: Often described as a custom cut, heart-shaped gemstones are very popular for pendants.

Marquise: According to legend, this shape was commissioned by King Louis XV to resemble the smile of his mistress, Marquise de Pompadour. Ideal marquise cuts have a length to width ratio of 2:1.

Oval: Similar to the round shape, oval gemstones produce a high amount of sparkle and fire.

Pear: This is a classic teardrop shape that is ideal for earrings and pendants.

Princess: This a relatively new shape that combines the sharp, flat edges of an emerald shape with numerous small facets, which produce both sparkle and fire.

Radiant: This shape is similar to emerald, but it adds extra facets on the edges and corners to increase the gemstone’s sparkle.

Round: This classic shape produces maximum sparkle and fire, making it an ideal shape for diamonds.

Tapered Baguette: A tapered baguette is a baguette shape with one end that is narrower than the other.

Trillion: A very striking, usually three-sided shape, trillion gemstones (especially diamonds) are celebrated for the intense fire they produce.

The Mohs Scale
The most common measure of a gemstone's degree of hardness is based on the Mohs Scale. Devised by German geologist Friedrich Mohs in 1812, the Mohs Scale grades minerals on a comparative scale from 1 (very soft) to 10 (very hard).

Hardness is generally associated with durability and the ability to resist breakage. When referring to gemstones, however, hardness more accurately means the stone's ability to resist abrasion. What the scale means is that a mineral of a given hardness rating will scratch other minerals of the same rating, as well as any minerals of a lower hardness rating. For example, rubies and sapphires, which are composed of the mineral corundum and have a Mohs rating of 9, will scratch each other, as well as topaz (rating 8) and quartz (rating 7). But they will not scratch diamonds, which are rated 10 and considered the hardest substance.

The numeric values assigned to each interval of hardness are not equal. Some stones are disproportionately harder than others. Because Mohs Scale wasn't made for exact precision, it uses half numbers for in-between hardness ratings.

Amethyst:

Amethyst, the most precious member of the quartz family, exhibits purple shades ranging from pale lilac to deep purple, sometimes exhibiting reddish or rose overtones. Very deep-colored amethysts are the finest and most highly valued. Some stones are so over-saturated with color they have areas that are blacked out, which can negatively impact their value. Paler shades, sometimes called "Rose of France," were common in Victorian jewelry. Banding—darker and lighter zones of color—is also a common occurrence. Occasionally, amethyst is even found combined with its sister quartz, citrine, into a single stone called ametrine.

The birthstone for February, amethyst is an extremely popular gem for jewelry because of its regal color, variety of sizes and shapes, affordability and wide range of hues. It also is the recommended gem for couples celebrating their 6th and 17th wedding anniversaries. With a hardness of 7.0 on the Mohs Scale , amethyst can occur as long prismatic crystals that have six-sided pyramids at either end, or can form as drusies that are crystalline crusts that only show the pointed terminations.

The ancient Greeks believed that amethyst made one immune to the effects of alcohol. In fact, the name even comes from the Greek word amethystos, which means “not drunken.” Legend has it that the amethyst originated from Bacchus, the god of wine. Bacchus became angry at the mortals and vowed that the next mortal to cross his path would be eaten by tigers. Amethyst, a beautiful young maiden, was on her way to worship the goddess, Diana. Diana turned her into colorless quartz to keep her from being eaten. Bacchus observed the miracle and repented his hasty decision. He poured wine over the young maiden, leaving her feet and legs colorless. This is the reason that amethyst crystals are usually uneven in color and have a colorless base at the bottom. Because amethyst was believed to prevent drunkenness, wine goblets were often carved from it in ancient Greece. Today, the gem still symbolizes sobriety.

Amethyst has been a part of history throughout the ages. Evidence suggests that prehistoric humans used amethysts for decoration as early as 25,000 B.C. Legends suggest that the Egyptian queen Cleopatra wore an amethyst signet ring, as did Saint Valentine, who bared an amethyst engraved with the figure of Cupid. During medieval times, people used the stone as medication to stay awake and alert. Leonardo Da Vinci claimed that amethyst could dissipate evil thoughts and quicken the intelligence. In some legends, the stone represents piety, celibacy and dignity. In the Middle Ages, for instance, the gem was an important ornamentation for the Catholic Church and other religions. It was considered the stone of bishops, and they still often wear amethyst rings. In Tibet, amethyst is considered sacred to Buddha and rosaries are often made from it. Amethyst has also long been a favorite of kings and queens for its royal purple hues that symbolize wisdom, strength and confidence. Amethysts are even featured in the British Crown Jewels and were worn by Catherine the Great.

Amethyst’s availability and magical qualities make it the stone of preference in ancient lore and mysticism. As a meditation stone, it is said to quiet the mind, promote contemplation, sharpen psychic powers and uplift the spirit. It is a stone of deep wisdom. Folklore says it can quicken the wit, calm fears, ward off anger and overcome alcoholism. It has a royal purple essence that is said to lend courage to travelers, scare off thieves and protect travelers from harm, sickness and danger. Placed under the pillow or worn to bed, there are claims it promotes peaceful sleep, pleasant dreams, and the healing of tired joints and muscles. Amethyst can also be worn to supposedly make the wearer gentle, amiable and happy.

The stone is mined in Brazil, Uruguay, Bolivia and Argentina, as well as in Zambia, Namibia and other African nations. Very dark amethyst in small sizes also is mined in Australia. But the ideal for fine quality amethyst was set by a Siberian variety, often called Russian or Uralian amethyst, which is now considered a defunct source. Generally, South American amethyst tends to come in larger sizes than African amethyst, but the African variety has a reputation for having deeper color intensity and is therefore considered more valuable. The African version also is harder to come by than amethyst mined from South America. Most of today's amethyst comes out of Brazil.