Sapphire is the mineral corundum. Blue ones are the second most popular of the world’s gems, after diamonds.
The grading and evaluation of sapphire is focused on their color. Gem quality blue sapphire is vivid medium dark blue, neither grayish nor greenish, and transparent on the clarity side of grading.
Lighter tones of blue are also very appealing and preferred by some. Dark tones often appear black in jewelry and are the least in value and desirability.
Some of our most beautiful pieces of jewelry over the years have featured sapphire, the screaming blue one in the 1st image is our “centerpiece” right now. Even though we have diamonds that cost more.