Celestine
“Sky-blue strontium crystal”
Mineral
Celestine (or celestite) is a delicate pale blue strontium sulfate mineral often found in stunning crystal geodes. It's the primary ore of strontium, an element used in fireworks to produce brilliant red flames and in the refinement of sugar from beet molasses.
Composition
strontium sulfate (SrSO₄)
Where Found
Crystal Cave (Put-in-Bay, Ohio, USA), Madagascar, Sicily (Italy), Turkmenistan, Bristol (England)
Mohs Hardness
3-3.5
Fun Fact
The world's largest known geode is a celestine-lined cave on South Bass Island, Ohio — it's 35 feet wide and you can walk inside it.
Test Your Knowledge
Why is celestine the only commercially viable ore of strontium despite other strontium minerals existing?
Related Specimens
Want to identify rocks yourself?