What are semi-precious gemstones?

In the western world, diamond, ruby, emerald, and sapphire are the four gemstones deemed precious. The remaining gems are called semi-precious, but this title doesn’t always reflect their value.
The ornamental use of jewelry and gemstones is deeply rooted in the history of humankind.
They developed personal, public, and spiritual meanings to men, gaining greater social importance as human civilizations became more evolved.