What is Corundum?
Lab-grown corundum is genuine corundum (Al₂O₃) that has been grown under carefully controlled laboratory conditions rather than formed naturally within the Earth's crust. Chemically, physically and optically, it is the same mineral as natural corundum.
Corundum is one of the hardest naturally occurring minerals, ranking 9 on the Mohs hardness scale, second only to diamond. Its exceptional hardness, durability and optical properties have made it one of the world's most important gemstone minerals.
The only difference between natural and lab-grown corundum is how the crystal formed. Natural corundum crystallises over millions of years during geological processes, whereas laboratory-grown corundum is produced over days or weeks in advanced technology laboratories using modern crystal-growth techniques that replicate the same crystal structure.
At Gemdrop®, every corundum gemstone is clearly identified, scientifically verified and supplied with a permanent verification record.
Ruby and Sapphire
Corundum occurs naturally in many colours.
The gemstone names depend primarily on colour.
- Ruby is the red variety of corundum, coloured by chromium.
- Sapphire is most commonly the blue variety of corundum, coloured primarily by iron and titanium.
- In modern lab gemology Sapphire [cornundum] occurs in a wide variety of colors as well as colour-change varieties.
At Gemdrop®, each colour variety is described separately so customers receive accurate scientific information about the gemstone they are purchasing.
Laboratory-Grown Corundum Colours
Modern crystal-growth techniques allow corundum to be grown in a wide spectrum of colours, including varieties of: blue, pink, yellow, green, white, purple, padparadscha, colour-change and red (ruby).
The colour is produced by introducing carefully controlled trace elements during crystal growth, replicating the natural causes of colour found in geological corundum.
Corundum Properties
Mineral: Corundum
Chemical Formula: Al₂O₃
Crystal System: Trigonal
Mohs Hardness: 9
Refractive Index: 1.760–1.770
Specific Gravity: ~4.00
Cleavage: None
Durability: Excellent
How Lab-Grown Corundum is Produced
Lab-grown corundum can be produced using several advanced crystal-growth techniques. At Gemdrop®, the most common methods encountered are:
- Flame Fusion (Verneuil Process)
- Czochralski Crystal Growth
Both Flame Fusion and Czochralski growth produce genuine crystalline corundum (Al₂O₃) with the same chemical composition and crystal structure as natural corundum. Flame fusion technology has advanced significantly in recent years and is capable of producing exceptionally beautiful, high-quality gemstones. However, Czochralski-grown corundum is generally regarded as the premium growth method, offering the highest levels of crystal quality.
The crystal-growth method for every GemDrop® gemstone is clearly disclosed at the point of sale and is permanently recorded in the gemstone's Gemdrop® Verification Record, providing complete transparency and long-term traceability.