It occurs as translucent, vitreous white to grey to yellow monoclinic prismatic crystals.

It is an unstable mineral which dehydrates in dry air and decomposes in water.

It also occurs rarely as veinlets in alkalic igneous rocks.

It was named for French chemist Joseph Louis Gay-Lussac (1778–1850).

[3] The mineral has been recently (2014) reported from drill core in Lonar lake in Buldhana district, Maharashtra, India.