RUBY
Ruby
Corundum
The red variety of corundum, colored by chromium. Sapphire belongs to the same mineral species.
GEM PROFILE
Basic properties
- Mineral or material
- Corundum
- Main chemical composition
- Al₂O₃
- Crystal & structure
- Trigonal
Natural crystals can form hexagonal plates or prisms. A crystal's visible outline does not necessarily share the name of its crystal system.
- Typical colors
- Red, purplish red and orangy red
- Mohs hardness
- 9
A measure of scratch resistance, distinct from resistance to impact or breakage.
About hardness and durability - Representative sources
Examples of known sources. Determining the origin of an individual stone requires examination and comparison with reference material.
- Common cutting styles
- Oval and cushion mixed cuts are common. Material showing a star is polished as a cabochon.
Explore cutting styles
LOOK A LITTLE CLOSER
What to observe
Observe the color distribution, transparency and inclusions such as fine needles. A red appearance alone does not establish a stone's identity or geographic origin.
TREATMENT & CARE
Treatments & care
Treatments & identification
Heating, impregnation and filling may be encountered. Natural versus synthetic identity is a separate question from whether a stone has been treated.
Everyday care
Avoid impacts and use care appropriate to the stone's condition. Wipe filled or dyed material with a damp soft cloth and ask a specialist before using cleaning equipment.
Cleaning depends on treatment, inclusions and mounting. If a stone's condition is unknown, ask your jeweler or a gem specialist before cleaning.
READING & REFERENCES
References
Public sources for learning about this gemstone's general properties.
- GIA · Gemological reference
- GIA · Care & Cleaning
- Handbook of Mineralogy · Mineral data (PDF)
- GIA · Gem sources and fundamentals
This dictionary provides general educational information. Values are representative and do not identify or grade an individual stone. Locality examples include historical deposits.
Sources checked: October 19, 2026