A red ruby gemstone is a precious gemstone that belongs to the corundum mineral family. Rubies are highly valued for their vibrant red color, which can range from a deep, rich red to a slightly purplish or orangish-red hue.

The most defining characteristic of a ruby is its red color. The finest rubies are often described as "pigeon's blood" red, which is a pure, intense red with no secondary colors. Ruby's color is caused by the presence of chromium in the gemstone.

Rubies are considered one of the "Big Four" gemstones, along with diamonds, sapphires, and emeralds. They are prized for their beauty, rarity, and durability, making them a popular choice for fine jewelry.