Meionite: The scapolite mineral meionite information and pictures

About

Meionite is the calcium-rich end member of the Scapolite series. It is very similar and often indistinguishable from Marialite, the other end member of the series. Intermediary forms of Meionite and Marialite are frequent, and these are classified simply as Scapolite. Of the two Scapolite minerals, Meionite is the more prevalent form. Meionite is named for the Greek word meion (μειον), which translates as "minus", in reference to its lesser termination angles when compared to Vesuvianite.

Crystal Forms & Aggregates

Crystals are often short and stout with a slightly angled or pyramidal termination, or long and prismatic. Crystals can be very large and fat, and are often intergrown in groups of such crystals or are columnar. Also grainy, massive, and crudely as formed crystal masses. Prismatic crystals are often striated.

Other ID Marks

Often fluorescent, sometimes brightly. Colors include white, yellow, and pink. Fluorescence may be present both in shortwave and longwave.

Striking Features

Crystal habit, environment, and fluorescence

Environment

Chiefly in metamorphic rocks, in metamorphosed limestones, skarns, gneisses, and hornfels. Also in granite pegmatites.

Noteworthy Localities

The two Scapolite members often occur together and are not usually individually distinguished. See Scapolite for a comprehensive list of localities general to the Scapolite series.

Common Mineral Associations

Diopside, Biotite, Phlogopite, Titanite, Hornblende, Actinolite, Almandine, Microcline, Muscovite

Distinguishing Similar Minerals

Meionite - Difficult to distinguish without chemical analysis.
Feldspars - Often form in different crystal habits, lacks fluorescence.
Nepheline - Different cleavage, lacks fluorescence.