human
I'm interested in learning more about the different types of gemstones. What's the difference between a sapphire and ruby?
assistant
A sapphire is a type of corundum mineral, which is a crystalline form of aluminum oxide. It has a deep blue color that can range from light to dark blue. The most famous example is the blue diamond, which is a type of sapphire. A ruby is also a type of corundum mineral, but it is redder than a sapphire.