A gemstone is a piece of mineral or crystal that's been cut and polished to make beautiful jewelry or decorative objects. Diamonds, rubies, emeralds, and sapphires are famous gemstones that people prize for their beauty, rarity, and durability. When a jeweler finds a rough gemstone in nature, it might look like an ordinary rock until it's carefully cut and polished to reveal brilliant colors and sparkle.

What makes a mineral become a gemstone? Three qualities matter most: beauty (striking colors or the way light plays through it), rarity (not easy to find), and hardness (tough enough to last in jewelry you'll wear for years). Diamonds are among the hardest natural substances on Earth, which is one reason diamond rings can be worn every day without scratching easily. Softer minerals like opal can still be gemstones, but they require more careful handling.

People have treasured gemstones for thousands of years. Ancient Egyptians wore lapis lazuli and turquoise. Medieval kings displayed rubies in their crowns to show wealth and power. Today, gemstones still mark important moments: many people receive a birthstone necklace that corresponds to the month they were born.

Some gemstones form deep underground under intense heat and pressure over millions of years. Others, like pearls and amber, come from living things (oysters and ancient tree resin). A few, like cubic zirconia, are manufactured in laboratories to look like natural gemstones but cost much less.