Edingtonite

edingtonite

thomsonite

harmotome

natrolite

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Formula: Ba(Si3Al2)O10.4H2O
Tectosilicate, zeolite group, barium-bearing mineral
Specific gravity: 2.694 to 2.71 measured
Hardness: 4 to 5
Streak: White
Colour: Colourless to white
Solubility: Gelatinises with acids
Environments

Igneous environments
pegmatites
Carbonatites
Hydrothermal environments

Edingtonite occurs as a late-stage hydrothermal mineral in cavities in mafic igneous rocks and nepheline syenites; in carbonatites and in hydrothermal ore veins. In England it occurs in dolerite (HOM, Dana). Associated minerals include thomsonite, analcime, natrolite, harmotome, brewsterite, prehnite and calcite (HOM).

Localities

The Ice River Alkaline Complex, Golden Mining Division, British Columbia, Canada, consists of a suite of ijolites, syenites, carbonatites and late-stage pegmatites.
Edingtonite occurs in isolated zeolite- and carbonate-rich pockets in nepheline syenites. It is a late-stage mineral in these pockets, which were, themselves, one of the last phases of the complex to form. The major constituents of the pockets are calcite, natrolite and edingtonite, with minor ancylite, catapleiite, aegirine, pyrite and galena (CM 22.253-258).

The Mount Mather Creek claim, Golden Mining Division, British Columbia, Canada, is a sodalite-bearing breccia dyke that consists of carbonate-rich syenite segregations that occur as veins and pods, and fine-grained banded sodalite plus carbonate fragments in a carbonate-rich matrix. The sodalite-carbonate segregations consist dominantly of sodalite, iron-bearing dolomite, calcite and microcline, with an extensive suite of trace minerals including albite, analcime, ancylite-(Ce), chabazite-Na, fluorapatite, baryte, barytocalcite, cancrinite, galena, goethite, gonnardite, harmotome, edingtonite, natrolite, nordstrandite, pyrite, quintinite and sphalerite. Alteration of the primary silicate–carbonate assemblage has resulted in a secondary assemblage including albite, analcime, cancrinite, gonnardite and nordstrandite after sodalite, together with complex intergrowths of ancylite-(Ce), barytocalcite, edingtonite, and a potentially new magnesium-bearing edingtonite-like mineral. Remobilisation of barium and strontium from barytocalcite resulted in crystallisation of late-stage baryte and strontium-rich calcite (MM 86.2.282-306).

At the Brunswick No. 12 mine, Bathurst Mining Camp, Bathurst Parish, Gloucester county, New Brunswick, Canada, the deposit is a massive sulphide body occurring in sedimentary and volcanic rocks. Edingtonite occurs in open fractures in veins, where the mineral assemblage is edingtonite, chalcopyrite, galena, pyrite, sphalerite, barytocalcite, calcite, dolomite, quartz, greenalite and lizardite, and is apparently derived from ascending hydrothermal fluids reacting with massive sulphides, argillites and siliceous tuffs (CM 22.253-258).

At Yukspor Mt, Khibiny Massif, Murmansk Oblast, Russia, edingtonite occurs with ferricerite-(La), barylite and other minerals (MinRec 35.2.176, 35.4.347).

At the type locality, the Kilpatrick Hills, Scotland, UK, edingtonite was found on Lord Blantyre's Estate, West Kilpatrick, Dumbartonshire, near Glasgow, Scottland, associated with prehnite, harmotome, calcite, analcime and thomsonite (Mindat).

Loanhead Quarry, Beith, North Ayrshire, Scotland, UK, works highly altered porphyritic basaltic lavas that are contemporaries of the andesitic lavas at the type locality for edingtonite 20 km away. Loose material collected close to the quarry face contained edingtonite associated with harmotome. The matrix consisted of thomsonite and pink and white analcime crystals, with specular and micaceous hematite and botryoidal prehnite. Partial dissolution of the matrix has left colourless to white irregular platy aggregates of prehnite.
Subsequently, in a prehnite vein intersected by a baryte vein, harmotome and edingtonite occurred in a contact alteration zone. The matrix of this zone was mainly massive prehnite intergrown with thomsonite and natrolite accompanied by baryte and calcite. Dissolution channels of prehnite and thomsonite/natrolite contained or were close to recrystallised natrolite, prehnite, baryte and calcite.
The edingtonite forms colourless, transparent, complex wedge-shaped crystals, frequently as intergrown aggregates. Sometimes edingtonite crystals are perched on, or are penetrated by, small well formed thomsonite needles, and occasionally they partially enclose harmotome. It also occurs as random single crystals in or on botryoidal prehnite. Tiny single crystals and intergrown groups of edingtonite with inclusions of hematite occur in close association with small rosettes of blood-red platy hematite, also on botryoidal prehnite. The edingtonite is closely associated with harmotome, thomsonite, natrolite, and very rare diaspore (JRS 6.27-30).

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