It typically occurs as radiating clusters or fibrous masses that are transparent to translucent in colors ranging from white through reddish and yellowish white to gray.

Typical occurrence is as an alteration and vesicle filling mineral in basalts.

The calcium variety was first described in 1821 for an occurrence in Dalsnipa, Sandoy, Faroe Islands.

The sodium variety was described in 1997 for an occurrence in Chojabaru, Nagasaki Prefecture, Japan.

This article about a specific silicate mineral is a stub.