Marialite, Meionite

specimen number:
2062312

location:
McGregor Lake, Quebec, Canada

description:
A loose double terminated crystal of marialite-meionite. Complete all around and in great condition. Collected in 1999.

The McGregor Lake area, located in the municipality of Val-des-Monts within the Gatineau region of Quebec, Canada, is a historic mining district recognized for its late-nineteenth and early-twentieth century mineral extraction. Geologically, the region lies within the Central Metasedimentary Belt of the Grenville Province, characterized by high-grade metamorphic rocks where complex pegmatites and pyroxenite intrusions hosted significant pocket-like deposits of phlogopite mica and apatite. Industrial mining in the vicinity of the lake began in the late 1870s and 1880s to supply raw phosphate for the international fertilizer market, shifting heavily toward high-quality phlogopite mica production by the 1890s as global phosphate prices collapsed. Numerous small-scale operations and deep pits, including the prominent Wallingford mine nearby, sustained steady output to support the burgeoning electrical insulation industry. This intense period of commercial operation peaked through the early 1900s, but declining yields and changing material demands led to a steady scale-back, with almost all formal extraction terminating by the onset of World War II.

The meionite-marialite series constitutes a continuous solid-solution framework within the scapolite mineral group, a collection of rock-forming aluminosilicates found primarily in metamorphic settings. Geologically, these minerals develop through high-grade regional or contact metamorphism, frequently crystallizing in calcium-rich environments like skarns, marbles, and altered mafic igneous rocks where hydrothermal fluids introduce volatile elements. Marialite represents the sodium-rich, chloride-bearing end-member of the series, while meionite anchors the calcium-rich, carbonate-bearing end-member. The chemical balance between these two points determines the specific structural density and refractive indices of the resulting tetragonal crystals, which commonly appear as distinct prismatic columns ranging from colorless and white to shades of yellow, grey, or pink depending on localized chemical impurities.

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