Gmelinite

Gmelinite is a mineral belonging to the zeolite group, characterized by its complex framework structure. It is a hydrous silicate of sodium, calcium, and aluminum, with the chemical formula generally represented as (Na, Ca)2[Al2Si4O12]·6H2O. Gmelinite crystallizes in the trigonal crystal system, often forming radiating aggregates or distinct prismatic crystals. Its color typically ranges from colorless to white, and it can also appear in shades of yellow or pink. The mineral is transparent to translucent and possesses a vitreous luster. It is relatively soft, with a Mohs hardness of 4 to 4.5, and has a specific gravity of approximately 2.1. Gmelinite is commonly found in cavities within volcanic rocks, such as basalts and andesites, where it forms as a secondary mineral. It can also occur in sedimentary rocks. Notable occurrences have been reported from various locations worldwide, including Ireland, Scotland, Iceland, and the United States. The mineral was first described in 1878 and named in honor of the German chemist and mineralogist Christian Gottlob Gmelin. Gmelinite is not considered an economically important mineral, but it is of interest to mineralogists and geologists due to its structural properties and occurrence in hydrothermal environments.