It's extremely rare, and this particular stone was valued ... While pearls are considered gemstones, they are not minerals but made of calcium carbonate by mollusks, such as oysters.

The Earth’s surface is also three-quarters water, and valuable gemstones like corals and ... than naturally-occurring pearls which are extremely rare. Just Curious: Answering your everyday ...

Pink diamonds are extremely rare and coveted — a now-closed mine in Australia has been the source of 90% of the colored gemstones. Polished pink specimens of the highest grade can sell for tens ...

Gemstones have been a topic of fascination ... Found mainly in Sri Lanka and Tanzania, taaffeite is extremely rare, with few known gem-quality specimens. Its accidental discovery and mysterious ...