Gemstones

Onyx: A Timeless Gemstone in Jewelry

Onyx is a captivating gemstone celebrated for its deep, uniform color and its historical significance in jewelry. While most commonly recognized in its black form, onyx is actually a variety of chalcedony, a cryptocrystalline form of silica, and can appear in a range of colors and banded patterns. Its accessibility, durability, and striking appearance have made it a popular choice for jewelry designers and consumers alike for centuries.

Definition

Onyx is a cryptocrystalline variety of silica, chiefly chalcedony, characterized by its parallel bands of color. The name originates from the Greek word 'onyx', meaning 'nail' or 'claw', likely referring to the gemstone's coloration resembling fingernails. True onyx, in gemological terms, has straight, parallel bands. When the bands are curved, the stone is referred to as sardonyx. However, in the modern jewelry market, the term 'onyx' most often refers to chalcedony that is uniformly black or a very dark gray.

Key Features

Color: The most prized onyx is uniformly black, without any undertones or other colored bands. However, it can also be found in white, gray, brown, red, orange, and green, often with parallel banding.
Luster: When polished, onyx typically exhibits a vitreous to dull luster.
Hardness: On the Mohs scale of hardness, onyx rates a 6.5 to 7, making it sufficiently durable for everyday jewelry wear, though it can be susceptible to scratching compared to harder gemstones like diamonds or sapphires.
Clarity: In opaque gemstones like onyx, clarity is not a primary concern. The focus is on the evenness and depth of color.
Cut: Onyx is often cut into cabochons (smooth, rounded shapes), beads, and intaglios (carvings in relief). Its opaque nature makes it ideal for carving and inlay work.
Diaphaneity: Onyx is an opaque gemstone, meaning light does not pass through it.

Origin and History

Onyx has a rich history stretching back to ancient civilizations. The Egyptians used onyx as early as the Second Dynasty to carve scarabs and inlay materials. The Romans also prized onyx, using it for carved cameos and intaglios, often depicting gods, heroes, or intricate patterns. It was believed to possess protective qualities, offering strength and courage to the wearer. During the Victorian era, black onyx became particularly fashionable, symbolizing mourning and remembrance, often set in jet or gold.

Types / Variations

While black onyx is the most common, other variations exist:

Black Onyx: The most sought-after variety, typically treated to achieve its deep black color.
Sardonyx: Characterized by parallel bands of sard (a reddish-brown chalcedony) and onyx (black or white chalcedony).
White Onyx: Naturally occurring white or light-colored chalcedony.
Green Onyx: Often dyed chalcedony, as natural green onyx is rare.
Blue Onyx: This is typically dyed chalcedony, as naturally occurring blue onyx is extremely uncommon.

It is important to note that much of the black onyx available today is actually chalcedony that has been dyed or treated to enhance its color. This is a common and accepted practice in the industry, but it is crucial for consumers to be aware of it.

How It's Made

Onyx is a natural gemstone formed over geological timescales through the deposition of silica in cavities within volcanic rocks. The characteristic banding is a result of the slow accretion of mineral-rich water. Modern onyx, particularly the uniformly black variety, often undergoes treatments to achieve its desired appearance. The most common treatment is dyeing. Chalcedony, which may naturally have bands or be lighter in color, is immersed in a sugar solution, then heated. The sugar solution permeates the stone, and subsequent chemical treatment carbonizes the sugar, turning the stone black. Other treatments may include impregnation with polymers to improve durability or color stability.

Grading & Quality Standards

Unlike transparent gemstones that are graded using the 4 Cs (color, clarity, cut, carat), onyx grading is simpler, focusing on:

Color: For black onyx, the ideal is a deep, uniform black with no visible undertones or inclusions. For banded onyx (like sardonyx), the distinctness and contrast of the bands are important.
Cut: The polish should be smooth and even, enhancing the stone's luster. The shape and symmetry of the cut are also considered.
Size: Larger stones are generally more valuable, especially if they exhibit good color and cut.
Inclusions/Banding: While uniform color is preferred for black onyx, natural banding or inclusions can be acceptable and even desirable in other varieties like sardonyx, provided they enhance the stone's unique beauty.

There isn't a standardized, universally accepted grading system like the 4 Cs for diamonds. Quality is often assessed subjectively based on the visual appeal.

Buying Guide

When purchasing onyx jewelry, consider the following:

Color: Decide if you prefer the classic deep black or a banded variety. Be aware that most black onyx is dyed.
Setting: Onyx is versatile and works well in various settings, from simple bezel settings that protect its edges to intricate metalwork. Consider how the metal color (yellow gold, white gold, silver) complements the onyx.
Durability: While moderately hard, onyx can chip or scratch. For rings, consider settings that offer protection, like bezel settings or lower-profile designs. Pendants and earrings are generally less prone to damage.
Treatment Disclosure: Reputable jewelers will disclose if the onyx has been treated (dyed, heated, etc.). Ensure you are comfortable with the treatments applied.
Price: Onyx is generally affordable, making it a great option for statement pieces or everyday jewelry without a prohibitive cost.
Authenticity: While treatments are common, be wary of overly unrealistic prices for exceptionally large or seemingly flawless stones, as they might be synthetic or imitations.

Price Range & Value Factors

Onyx is considered an affordable gemstone. Its price is influenced by:

Color and Uniformity: Deep, uniform black onyx commands a higher price than stones with visible bands or lighter tones.
Size: Larger stones naturally cost more.
Cut and Polish: A well-cut and highly polished stone will be more valuable.
Origin: While onyx is found globally, certain sources might be more desirable, though this is less of a factor than with precious gems.
Treatments: Dyed onyx is standard; the price is generally consistent for treated stones. Natural, untreated onyx, if available and of good quality, might command a premium but is rare.

Prices can range from a few dollars for simple beads to hundreds or even thousands of dollars for large, intricately carved pieces or fine jewelry featuring high-quality onyx, especially when paired with precious metals and other gemstones.

Care and Maintenance

Proper care will ensure your onyx jewelry retains its beauty:

Cleaning: Clean onyx with a soft brush, warm water, and mild soap. Avoid harsh detergents or ultrasonic cleaners. Rinse thoroughly and dry with a soft, lint-free cloth.
Avoid Harsh Chemicals: Keep onyx away from household cleaners, perfumes, hairsprays, and cosmetics, as these can damage the stone's surface or dull its luster.
Protection: Store onyx jewelry separately to prevent scratching from harder gemstones or metal components.
Avoid Impact: Due to its moderate hardness, avoid subjecting onyx to hard knocks or impacts that could cause chipping or cracking.
Re-polishing: If the polish becomes dull over time, a jeweler can re-polish the stone.

Pros and Cons

Pros:

Affordability: Onyx is a budget-friendly gemstone.
Striking Appearance: Its deep black color offers a sophisticated and bold look.
Durability: It's hard enough for most types of jewelry, especially when set protectively.
Versatility: It suits various styles, from classic to modern, and works well with different metals.
Carving Potential: Its opaque nature and moderate hardness make it excellent for intricate carvings, cameos, and intaglios.

Cons:

Susceptible to Scratches: Softer than many precious gemstones, it can scratch or chip if not cared for properly.
Common Treatments: Most black onyx is dyed, which may not appeal to those seeking entirely natural stones.
Opaque Nature: Lacks the fire and brilliance of transparent, faceted gemstones.
Potential for Imitation: Easily imitated by glass or other dark materials.

Famous Examples

Onyx has been a favorite for historical carvings and adornments. While specific famous pieces often lack documented details beyond their historical context, notable uses include:

Ancient Roman Intaglios and Cameos: Many surviving artifacts from the Roman Empire feature onyx, showcasing detailed carvings of mythological figures, emperors, and scenes. These are often found in museums and private collections.
Victorian Mourning Jewelry: Black onyx was extensively used in lockets, brooches, and rings during the Victorian era, often combined with jet or seed pearls, as a symbol of remembrance and grief.
Modern Designer Pieces: Contemporary jewelry designers frequently incorporate onyx into collections, appreciating its bold contrast and masculine appeal, often pairing it with diamonds or contrasting colored gemstones.

Common Misconceptions

All Onyx is Black: While black is the most common and recognized color, onyx can occur naturally in banded forms (like sardonyx) and lighter colors.
Onyx is Extremely Durable: With a Mohs hardness of 6.5-7, it is durable enough for jewelry but is more prone to scratching and chipping than harder stones like sapphire or diamond.
Dyed Onyx is Fake: Dyeing is a common and accepted treatment to enhance the color of chalcedony to achieve the desirable deep black onyx. It does not make the stone