Diamond is the world’s most famous and valuable precious gemstone, celebrated for its unmatched brilliance and durability. It is made entirely of crystallized carbon and is the hardest natural substance known. 

Sapphire is a precious gemstone best known for its deep blue color, though it actually comes in many hues, including pink, yellow, green, and even colorless. Only red corundum is called ruby—all other colors are sapphire. 

Ruby is a precious gemstone known for its vivid red color, ranging from pinkish to deep blood-red. It is the red variety of the mineral corundum—all other colors of corundum are called sapphire. 

Emerald is a highly valued green gemstone known for its rich, vibrant color. It belongs to the beryl mineral family, with its green hue caused by traces of chromium or vanadium.