Natrolite after Nepheline

specimen number:
2133059

location:
Poudrette Quarry, Mt. St. Hilaire, Quebec, Canada

description:
Large blocky terminated crystals of what were once nepheline, these now replaced by crystallized natrolite. Interesting pseudomorph specimen for the locality.

A pseudomorph is a mineral specimen in which one mineral has replaced another while preserving the original crystal shape. In the case of natrolite after nepheline, the original nepheline crystals were gradually altered by hydrothermal fluids that introduced sodium and silica, causing natrolite to form while retaining the external form of the nepheline crystals. These pseudomorphs are commonly found in alkaline igneous environments such as nepheline syenites and related pegmatites. The resulting specimens show the crystal shape of nepheline but are composed internally of natrolite.

Mont Saint Hilaire is a well known mineral locality located near Montreal in Quebec, Canada. It is an alkaline igneous complex that formed about 125 million years ago and is part of the Monteregian Hills. The area is famous among mineral collectors for its exceptional mineral diversity, with more than 400 identified mineral species, many of them rare or first discovered at the locality. Most specimens come from the Poudrette Quarry, where minerals formed in cavities within nepheline syenite and related rocks. Mont Saint Hilaire is considered one of the worlds most important localities for rare mineral species.

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