Spinel

Spinel: The Renaissance of a Historical Gemstone Long overshadowed by ruby and sapphire, spinel is now recognized as an exceptional gemstone by collectors and experts alike. Scientifically, it is a magnesium aluminum oxide with the formula MgAl₂O₄. It belongs to the cubic crystal system, frequently appearing as perfect octahedrons with smooth faces. With a Mohs hardness of 8, it offers remarkable resistance and durability, making it ideal for all jewelry designs.

A Chemistry of Intense Colors Spinel is an allochromatic stone: when pure, it is colorless, but it adopts vibrant hues through the integration of trace elements within its crystal lattice:

• Chromium (Cr³⁺): Responsible for fiery reds (the famous "spinel red") and intense pinks.

• Cobalt (Co²⁺): The source of electric blue spinels, among the rarest and most sought-after varieties in the world.

• Iron (Fe²⁺): Influences gray, violet, and deeper blue tones.

• Optics: Unlike ruby, spinel is singly refractive (isotropic). This means it exhibits no pleochroism; its color is perfectly consistent and saturated regardless of the viewing angle, simplifying the lapidary's orientation work.

Laboratory Analysis and Authenticity Historically, confusion was so prevalent that famous jewels, such as the "Black Prince's Ruby" in the British Crown Jewels, are actually spinels.

• Inclusions: During expertise, we identify natural spinel by its inclusions of small spinel or magnetite octahedrons, often aligned along growth axes.

• Synthesis: It is crucial to distinguish natural specimens from synthetic spinels (often produced by the Verneuil or flux methods), which are very common in vintage jewelry.

Care and Maintenance While robust and generally resistant to heat and common chemicals, spinel should be handled with care. Cleaning with lukewarm soapy water is sufficient to preserve its vitreous luster. It generally withstands ultrasonic cleaning well, provided it does not contain significant internal fractures.