Key Information
Gemstones
| Type | Gemstones |
| Precious Gemstones | Emerald, ruby, sapphire and diamond |
| Most Valuable Gemstone | Blue Diamond ($3.93 million per carat) |
Learning Point
- Gemstones have been sought after by humans from the beginning of human history, with some extremely valuable because of how rare they are. There are many famous gemstones, but in modern times we are finding even rarer gemstones as we explore more of our planet.
Project
- Draw your favourite gemstone, and a picture of who you would give it to.
- Overview
- Blue Diamond

Precious and Semiprecious Gemstones:
(clockwise from top left) diamond, uncut synthetic sapphire, ruby, uncut emerald, and amethyst crystal cluster.

The Hope Diamond
Science Week – 2024
Fun Facts
- Emerald, ruby, sapphire and diamond are the only gemstones called “precious” though other “semi-precious” stones might be more valuable.
- The Mohs scale is used to test the hardness of minerals.
- Gemstones are normally mineral crystals, but can include rocks and organic materials such as lapis lazuli, amber and pearl.
- Some gemstones are variations in colour of the same minerals, such as ruby and sapphire.
Past Lessons
| 102 | February 19, 2024 | (North America) |