Formula: Na(AlSi2O6).H2O
Tectosilicate (framework silicate), zeolite group, feldspathoid, forms series with pollucite and with wairakite (ZW).
Crystal System: Triclinic
Specific gravity: 2.24 to 2.29 measured, 2.271 calculated
Hardness: 5 to 5½
Streak: White
Colour: White, colourless, gray, pink, greenish, yellowish; colourless in thin section.
Solubility: Moderately soluble in hydrochloric acid

Igneous environments
Sedimentary environments
Basaltic cavities

Analcime occurs as a primary mineral in some igneous rocks; it is the only zeolite that crystallises directly from molten rock. In pegmatites and miarolytic cavities cesium-rich analcime forms from 250° to 150°C. Analcime phenocrysts crystallise in deep basaltic magma chambers at temperatures between 600 and 640°C, and at pressures from 5 to 13 kilobars. Rapid vertical transport to the surface is required for analcime to survive the decrease in temperature and pressure. A slow decrease in temperature and pressure would allow the analcime to react with the basaltic magma to produce albite (ZW).
Analcime is also the product of hydrothermal action in the filling of basalt cavities, where analcime phenocrysts crystallise in deep basaltic magma chambers at temperatures between 600oC and 640oC, and pressure between 5 and 13 kbar, in association with prehnite, calcite and zeolites such as chabazite, thomsonite and stilbite (DHZ 4 p346).
Geothermal wells have been drilled through a thick series of basalt flows in western Iceland, where it was found that analcime crystallised at temperatures from to 300oC at depths between 72m and 1600m (ZW).
Analcime may occur in mafic rocks such as aegirine-analcime-nepheline syenite.
In saline alkaline lakes, analcime forms near the centre of the lake, where the water is highly saline with pH 9 to 10 (strongly alkaline), and in these conditions analcime, K-feldspar, trona and borosilicates are dominant. Analcime forms at a higher pH (more alkaline) by dissolving phillipsite, erionite, chabazite, or silica-rich heulandite that crystallised when the pH was lower (less strongly alkaline) (ZW).
In deep sea sediments phillipsite and heulandite alter to analcime over a period of millions of years (ZW).
In lake beds, analcime may be altered from pyroclastics or clay minerals, or it may be a primary precipitate. It is authigenic (formed in place) in sandstone and siltstone.

Analcime crystallises in the isometric system, point group 4/m 3 2/m, and crystals usually have the form {211} (trapezohedron) Mindat Image


In Western Tasmania, Australia, analcime occurs as a late stage primary mineral with gonnardite-natrolite and as an alteration product of feldspar. It also occurs in basaltic cavities ( AJM 10.2.62-63 ).

In the Marron Volcanics of the Olalla Area, South-Central British Columbia, Canada, analcime is found lining many of the vesicles in the road cuts at Yellow Lake. These are clear to translucent, colourless crystals, commonly overgrown by a transparent to pinkish second generation analcime (R&M 96.6.519).

In the vicinity of Meshkinshahr, Ardabil Province, Iran, crystals of analcime are found embedded in small amygdules in potassium-rich basalt, associated with chabazite, mesolite and/or thomsonite. The analcime originated hydrothermally (R&M 92.6.541).

At Mount Kahoven, Semnan Province, Iran, orange coloured crystals of analcime are found on perched on vesicular basalt (R&M 92.6.542).

In the alkaline rocks of the Kola peninsula, Russia, analcime is associated with aegirine and may be either primary or secondary after sodalite or aegirine (DHZ 4 p345).

At Palabora, Limpopo, South Africa, analcime is an early phase in the deepest parts of the dyke fracture zone. Crystal cores may have originally been wairakite overgrown by analcime, then later hydrothermal alteration converted wairakite to laumontite. A later generation of analcime occurs on fluorapophyllite (R&M 92.5.433).

At Copthill Quarry, Stanhope, County Durham, England, UK, crystals of analcime on dolerite have been found (JRS 21.6).

At Cambokeels Mine, Westgate, Stanhope, County Durham, England, UK, analcime crystals typically up to 2 mm across occurred coating surfaces of dolerite. In many specimens the analcime was accompanied, and locally overgrown by, small crystals of apophyllite, and in a few specimens was also accompanied by crystals of calcite up to 2 mm across (JRS 21.6).

At the High Force Quarry, Forest and Frith, County Durham, England, UK, analcime crystals up to 1 mm across were found in samples as crusts up to 12 cm across coating joint surfaces of dolerite pegmatite. In some examples the analcime was accompanied by a few crystals of chabazite up to 2 mm across. Exactly similar small analcime crystals were also noted in situ in narrow stilbite - bearing veins in slightly chloritised dolerite pegmatite exposed in the quarry (JRS 21.6).

At Croft quarry, Croft, Leicestershire, England, UK, analcime has been found in a zeolite-filled fissure in tonalite, together with chabazite. The first generation of analcime occurs as crystals to 1mm associated with quartz. The second generation analcime crystals were numerous and larger, up to 13 mm across, associated with calcite, marcasite, chalcopyrite or galena. It is suggested that the analcime was produced by the action of water on feldspar:

plagioclase + water → analcime + laumontite + quartz

Both generations of analcime may enclose, or be coated with, hematite. Analcime and calcite may form pseudomorphs after laumontite (JRS 20.6-9, RES p185 to 190).

At Enderby Warren Quarry, Enderby, Blaby, Leicestershire, England, UK, analcime occurs in quartz-diorite and tonalite associated with laumontite (JRS 20.9).

At the Emmons pegmatite, Greenwood, Oxford county, Maine, USA, analcime has been identified in the central portion of lepidolite veins cutting pollucite masses. After pollucite has formed no more cesium is available, thus only analcime can form. The Emmons pegmatite is an example of a highly evolved boron-lithium-cesium-tantalum enriched pegmatite (R&M 94.6.503).

The Central Mine, Central, Keweenaw county, Michigan, USA, initially targeted a series of sub-parallel mineralised fissure veins where the most copper-rich portion of the vein was close to the base of the main greenstone flow.
Analcime from the Central mine occurs only as mediocre, opaque cream to white crystals up to 2 cm, commonly associated with other zeolites. Some Central mine analcime crystals contain inclusions of copper and/or hematite (MinRec 54.1.53-81).

At the Copper Falls Mine, Copper Falls, Keweenaw county, Michigan, USA, mineralisation occurs primarily in hydrothermal veins cutting preexisting lavas and as amygdules in the Ashbed flow.
Analcime is a fairly common zeolite mineral here; reddish crystals to 1 cm or so have been found in most of the veins at Copper Falls, sometimes associated with natrolite. These red analcime crystals were known from as early as the 1800s. White crystals, more typical for the species, are also not uncommon. Analcime with copper inclusions is also known from this locality (MinRec 54.1.94-95).

The Cliff Mine, Phoenix, Keweenaw county, Michigan, USA, is situated at the base of a roughly 70-metre basalt cliff. A curious feature of the impressive thickness of the greenstone flow here is that it contains zones of “pegmatoid”: areas where slow cooling in the core of the lava flow allowed for large feldspar crystals exceeding 1 cm to grow. Such features are normally only observed in intrusive igneous rocks and are almost unheard of in basalt flows.
The Cliff mine primarily exploited rich copper mineralisation in the Cliff fissure (vein). Although mineralised with copper to some extent along its entire length, the part of the vein just below the greenstone flow carried the richest copper mineralisation by far. A significant amount of the copper recovered at the Cliff mine came from amygdaloids in the tops of 13 basalt flows which were cut by the Cliff vein. The discovery and mining of this vein proved that the veins were the source of the large masses of float copper that were already well known, and proved that the primary ore mineral in the district was native copper, not sulphides, as had been suspected earlier.
Analcime is an uncommon mineral in the Cliff fissure, occurring as white or colourless crystals with typical trapezohedral habit to 1 or 2 cm. It is typically associated with quartz, prehnite, datolite, apophyllite, laumontite and copper (which is sometimes included in the analcime) (MinRec 54.1.25-49).

At the Phoenix Mine, Phoenix, Keweenaw county, Michigan, USA, mineralisation occurs primarily in hydrothermal veins cutting pre-existing Portage Lake basalts as well as in amygdules in the Ashbed basalt flow, and the vast majority of collectible minerals occur in the hydrothermal veins.
Superb examples of analcime associated with well crystallised copper, silver, calcite and a host of other minerals have been found here. Analcime is a common late-stage zeolite species in the veins. It typically occurs as opaque white trapezohedral crystals, exceptionally to 4 cm, on a matrix of other minerals. The analcime crystals often contain visually striking inclusions of other minerals, most notably native copper and hematite. Analcime crystals with oriented hematite inclusions and/or apophyllite coatings are a particular Phoenix mine specialty, as are the complex crystals with re-entrant edges which were first described (incorrectly) as twins; they are actually oriented overgrowths of colourless analcime on pre-existing white analcime crystals. These seem to be unique to the Phoenix mine (MinRec 54.1.125-130).

At the Bearpaw Mountains, Montana, USA, analcime occurs in cavities in igneous rock, associated with axinite, prehnite and datolite (DHZ 4 p345).

The Purple Diopside Mound, Rose Road, Pitcairn, St. Lawrence county, New York, USA, is situated in marble. The development of veins of large crystals probably occurred as a result of fluid penetration from a concurrent intrusion. Many of the minerals of interest to collectors formed during this primary event, with additional species resulting from the subsequent alteration of scapolite. There seems to be little, if any, secondary, late-stage mineralisation present.
Analcime occurs uncommonly as white, crude trapezohedral crystals in the walls of the scapolite vein. It most likely formed as an alteration of marialite (R&M 96.6.548). The analcime fluoresces pale yellow under long wave UV (R&M 97.5.442).


analcime to jadeite and H2O
Na(AlSi2O6).H2O → NaAlSi2O6 + H2O
At high temperature analcime changes to jadeite (ZW)

analcime and quartz to albite and H2O
Na(AlSi2O6).H2O + SiO2 ⇌ Na(AlSi3O8) + H2O
High temperature favours the forward reaction (JVW p 144, ZW).

nepheline and H4SiO4 (silicic acid) to analcime and H2O
NaAlSiO4 + H4SiO4 ⇌ Na(AlSi2O6).H2O + H2O (

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