opal

Everyday

1. An opal is a precious stone that shows flashing rainbow colours when you move it in the light. tree →
2. Opal is the material itself, a kind of hardened silica that contains water. tree →
3. Opal is also a milky, pale colour. tree →

In the lessons

In science lessons on rocks and minerals it is an example of a gemstone; Australia produces most of the world's opal, and Coober Pedy is a famous opal-mining town where people live underground. In stories an opal is a treasure. Phrases: «an opal ring», «black opal», «opal mine».

Examples

• Nan has an opal ring that sparkles blue and green. tree →
• Most of the world's opals come from Australia. tree →
• In Coober Pedy, miners dig for opal and some families live in underground houses. tree →
• The black opal is Australia's national gemstone. tree →
• When I tilted the opal, colours flashed like a tiny rainbow. tree →
• Opals contain water, so they can crack if they dry out. tree →
• The bathroom glass had a milky opal colour. tree →
• It is more precious than emeralds, and dearer than fine opals. tree →

Note

Countable for a stone (an opal, opals), uncountable for the material (made of opal). Use «an» because it starts with a vowel sound. Opal is the birthstone of October in many lists.