Gyrolite is a relatively rare member of the Zeolite group. Its color is commonly white or colorless, and less commonly green or brown. Its luster can range from vitreous to earthy depending on the quality of the crystalline form. An interesting habit is its tendency to form inside of volcanic bubbles (vesicles), or more commonly referenced as, cavities. This setting creates extremely aesthetic presentations and provides natural protection for the mineral crystals. In these cavities, as well as other matrixes, this unique mineral is associated with other numerous quality and contrasting minerals, including Okenite, Prehnite, Calcite, Quartz and Apophyllite.
The crystal system for Gyrolite is triclinic, typically forming nodular, spherical or radial aggregates that can appear glassy, dull or even fibrous. These aggregates form in individual nodules as opposed to botryoidal or encrusting forms. The crystal growths within these aggregates include compact, lamellar (scaly) and platy.
Notable localities for quality Gyrolite specimens include Greenland, India, Italy, Ireland, Scotland and the USA (California).