Jewelry Central
Jewelry Central: Ruby
This commercial site gives information on rubies, including their physical properties and where they are found. Includes some details on how to choose a ruby for purchase.
Jewelry Central
Jewelry Central: Gemstones
This commercial site contains general information on various synthetic and natural gemstones and provides links to specific gems.
Wikimedia
Wikipedia: Ruby (Gemstone)
This site from the Wikipedia encyclopedia gives a definition and information on hardness, value determination, and natural versus artificial rubies. Links are provided throughout for additional information on related subjects.
Curated OER
Rubies
This commercial site gives information on rubies, including their physical properties and where they are found. Includes some details on how to choose a ruby for purchase.