The image compares the properties of spinel and ruby, two red gemstones that are often confused with each other. Here’s a breakdown of the key differences:

• Chemical Composition: Spinel is magnesium aluminum oxide while ruby is aluminum oxide.
• Hardness: Spinel is 8 on the Mohs scale while ruby is 9, making ruby slightly more scratch resistant.
• Color: Both gems can come in a variety of red hues, but ruby generally has a deeper and richer red color, while spinel can also be pink or orange.
• Fluorescence: Spinel has a subtle glow, while ruby has a strong fluorescence.
• Availability: Spinel is more abundant than ruby.
• Price: Spinel is generally more affordable than ruby.

Historically, spinel was often mistaken for ruby. For example, the “Black Prince’s Ruby” in the British Crown Jewels is actually a spinel. Today, spinel is prized for its own beauty and affordability.