Glauberite

Glauberite is a sodium calcium sulfate mineral with the formula Na₂Ca(SO₄)₂, which forms as an evaporite. It is named for the closely related Glauber's salts. Because of its solubility, glauberite is often dissolved away from the crystal matrix leaving a mould into which other minerals are deposited giving them an anomalous crystal form.

References

* Webmineral
* Mindat

List of minerals