Gemstone Quality Values
An element isn’t automatically categorized as a gem just because it has been used in jewelry or because it’s a mineral. Materials like seeds, bones, and hair have all been a part of jewelry, but that doesn’t place them in the same group as pearls, rubies, and amber.
To be considered a gemstone, a material must share three necessary qualities with all other gems: beauty, rarity, and durability. Each quality, however, characterizes an array of possibility, so all gemstones have different grades of these three traits.
Over the centuries, gemstones have been cherished for their color and gleam. It is always difficult to classify what’s beautiful and what’s not as it delights the senses or appeals to the mind. The conventional definition of color is a combination of three qualities.
Color is a critical factor in a colored stone’s beauty. Color is the first thing to be noticed about the gemstone. Three color factors play a major role in determining the value of a gemstone.
• Hue - The first impression of an object’s primary color
• Saturation – A color’s strength and intensity
• Tone - Degree of darkness or lightness of a color
Clarity is the gemstone’s comparative freedom from blemishes and inclusions. An inclusion is defined as anything that interferes with the natural passage of light. There are three primary types of inclusions.
• Breaks – Often look white and feathery
• Hollow Area – Empty from inside
• Bits of Mineral – Mineral bubbles inside
A sliding scale, rarity means some gems are rarer than other gems. A few stones are so precious that they are categorized as collector’s items. Most gemstones fall somewhere in the middle of the rarity scale.
A human contribution to the appearance of a colored gemstone, the cut of the gem will display its value in shape and facet count. It supports the other three value factors of color, clarity, and carat of the colored gemstone. There are three basic cuts.
• Brilliant Cut - Features triangular or kite-shaped facets that radiate from the center toward the widest part of the cut stone.
• Step Cut - Utilizes mainly square and rectangular facets arranged in concentric rows.
• Mixed Cut - A cutting style that combines brilliant cut and step cut facets.
For many gemstones, the color and carat weight are the most significant value factors. Carat is the unit of measurement concerning the weight of the gemstone. Typically speaking, the bigger the gem, the higher the price.
• Metric Carat - The international measurement unit for gem weight (1 carat equals 0.20 gram).
• Point - One one-hundredth of a carat (0.01 ct.)
• Carat Total Weight - The combined weight of all stones in a piece of jewelry.
• Per-Carat Price - The price of the gem divided by its carat weight.
Durability is a gemstone’s ability to withstand wear and tear and its resistance to heat, light, water, and household chemicals. It is a combination of three factors.
• Hardness - How well a gemstone resists scratching and abrasion, measured on the Mohs scale of hardness.
• Toughness - How well a gemstone resists breaking, chipping, and cracking.
• Stability - How well a gemstone resists the effects of light, heat, humidity, and chemicals.