The Dual Identity of Ruby and Sapphire

Corundum, the second hardest natural mineral, is known as ruby when red and sapphire in other colors. Both gemstones are highly durable and scratch-resistant, making them suitable for various applications. Despite their identical composition, rubies contain trace amounts of chromium, giving them their red color, while different internal structures are created during manufacturing. End users often do not realize that these gemstones are composed of the same material.

Characteristics

Hardness
With a hardness of 9 on the Mohs scale, corundum is second only to diamond. This exceptional hardness allows it to effectively resist scratches and surface wear during high-pressure waterjet cleaning, ensuring the nozzle maintains its precision and shape.
Wear Resistance
Corundum’s high mechanical strength enables it to withstand the impact and pressure of high-pressure water flow without cracking or deforming. This strength ensures the nozzle’s stability and reliability in demanding high-pressure environments.
Wear Resistance
Known for its excellent wear resistance, corundum retains its shape and performance over extended periods of high-pressure waterjet cleaning. This reduces the frequency of nozzle wear and replacement, enhancing operational efficiency.
Surface Smoothness
When processed, corundum achieves a very smooth surface, which helps to reduce water flow resistance and increase cleaning efficiency. Additionally, the smooth surface minimizes the wear caused by particles in the water flow on the nozzle.

Physical and Mechanical Properties

PropertiesUnitValue
Structure/Single Crystal
Chemical Formula/Al2O3
Index of refraction/No: 1.768 (c-axis)Ne: 1.760 (c-axis)
Infrared of penetrable index%>85
Specific Gravityg/cm33.97
Theoretical Density%99.98
HardnessMohs9
Tensile StrengthGPa0.19
Compressive StrengthGPa2.1
Flexural StrengthGPa340~380
Dielectric Constant 11.5 parallel to C-axis9.3 perpendicular to C-axis
Dielectric StrengthV/cm48000
Melting Point°C2000
Coefficient of Expansion°C4.3 x 10-6/°C (perpendicular to C-axis)5.4 x 10-6/°C (parallel to C-axis)
Specific HeatJ/kg.°C750