Ranging from pastel sky blue to deep velvety royal and cornflower blue, caused by intervalence charge transfer between...
Chemical formula
Al₂O₃ + Fe²⁺/Ti⁴⁺ (Aluminum Oxide with Iron and Titanium intervalence charge transfer)
Corundum • Corundum
Ruby
Pure vibrant red to slightly purplish red; colored by trace chromium substituting for aluminum in the crystal lattice. Fluorescence under ultraviolet light is common in low-iron marble-hosted rubies.
Al₂O₃ + Cr³⁺ (Aluminum Oxide with trace Chromium)Mohs 9.0 Mohs
Mineralogical & Gemological Profile
| Mineral Family | Corundum |
|---|---|
| Mineral Species | Corundum |
| Gemological Variety | Ruby |
| Chemical Composition | Al₂O₃ + Cr³⁺ (Aluminum Oxide with trace Chromium) |
| Crystal System | Trigonal (Hexagonal scalenohedral) |
| Mohs Hardness | 9.0 Mohs |
| Specific Gravity | 3.97 – 4.05 |
| Refractive Index | 1.762 – 1.770 (Birefringence 0.008–0.010) |
Color Characteristics & Optical Behavior
Pure vibrant red to slightly purplish red; colored by trace chromium substituting for aluminum in the crystal lattice. Fluorescence under ultraviolet light is common in low-iron marble-hosted rubies.
Geological Context & Pakistani / Global Localities
Forms in high-grade metamorphic marble deposits (such as the Himalayan belt including Hunza, Pakistan; Jegdalek, Afghanistan; and Mogok, Myanmar) as well as amphibolite and alkali basalt environments.
Collector Interest & Rarity Factors
High-saturation red rubies—especially marble-hosted crystals with natural silk (rutile needles) and strong red UV fluorescence—are among the rarest collector gemstones globally.
Fine Jewelry Applications
Exceptional toughness and hardness (9.0 Mohs) make ruby ideal for daily-wear rings, heirloom pendants, bracelets, and bespoke high jewelry.
Treatment Considerations & Disclosure
Thermal enhancement (heat treatment) is widespread in the global trade to improve color and dissolve silk. Flux-healing and lead-glass fracture filling also exist and dramatically affect value. FADI Gems never assumes a ruby is unheated without laboratory verification.
Care & Cleaning Instructions
Clean with warm soapy water and a soft brush. Ultrasonic and steam cleaners are only safe for unfractured or standard heat-treated stones; never use ultrasonic cleaning on fracture-filled or flux-healed rubies.
Traditional Meaning
Traditional Symbolism & Cultural Heritage
Historically known in Sanskrit as 'Ratnaraj' (King of Precious Stones), ruby has traditionally symbolized vitality, nobility, and enduring devotion. It is the traditional July birthstone.
Note: Cultural and birthstone traditions are presented strictly as historical folklore, never as scientifically verified medical or metaphysical effects.
Corundum
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Chemical formula
Al₂O₃ + Cr³⁺ (Aluminum Oxide with lower trace Chromium concentration than Ruby)
Pale lemon yellow to rich canary and golden amber hues.
Chemical formula
Al₂O₃ + Fe³⁺ (Aluminum Oxide with trace Ferric Iron and color centers)