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.
Often referred to as the “Queen of Garnets,” rhodolite is the violet-red variety of the garnet family. Its most prized color is a beautiful raspberry, but the gem can also be found in shades of pink, red and wine. The name is derived from the Greek words “rhodon” and “lithos,” meaning rose-stone, which connects the gemstone today with the raspberry-pink flower known as the rhododendron.
Rhodolite is a combination of almandine and pyrope garnets. Although it is occasionally found in volcanic rock, the stone is most often found in alluvial deposits in the form of water-worn pebbles. For this reason, large solitaires weighing 5.00ct or more are seldom seen at retail. Most rhodolite is mined in Sri Lanka, Tanzania and Zimbabwe. It ranks a 7.5 on the Mohs Scale and is ideal for jewelry.
The ancients wore rhodolites as amulets for protection from injury or death in battles. Modern folklore says rhodolite can help one understand dreams, as well as bring about love and devotion when given as a gift.