Milarite

milarite

bertrandite

bavenite

titanite

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Formula: KCa2(Be2AlSi12)O30.H2O
Cyclosilicate (ring silicate), osumilite group
Specific gravity: 2.51 to 2.56
Hardness: 6
Streak: White
Colour: Colourless, white, greenish white, yellowish white
Solubility: Generally insoluble in common acids, some is slightly soluble in hydrochloric acid; soluble in HF (Dana)
Common impurities: Na
Environments:

Pegmatites
Hydrothermal environments

Milarite can form in solutions of pH ranging from 7 (neutral) to 9 (slightly alkaline). The best crystals come from the more alkaline environments. In some cases milarite is a product of the alteration of beryl in pegmatites. In Alpine-type clefts milarite occurs chiefly in intrusive bodies of syenite or in miarolytic cavities in aplite veins, commonly associated with orthoclase, actinolite, titanite, calcite, apatite, zeolites and, in some cases, quartz. Chlorite group minerals coat and partially replace milarite in many specimens (Minrec 35.5.405-418). Milarite is a low-temperature hydrothermal mineral crystallising at 200 to 250oC and low pressure (Dana). Other associated minerals include orthoclase, albite, fluorite, beryl, phenakite, bertrandite, bavenite, minasgeraisite-(Y), quartz, calcite, muscovite and chlorite (HOM).

Localities

At the Haitzingalmstollen, Bad Gastein, St. Johann im Pongau District, Salzburg, Austria, milarite crystals to 4 mm are associated with titanite (Minrec 35.5.410).

At Wiesbachrinne, Bramberg am Wildkogel, Zell am See District, Salzburg, Austria, cabinet sized specimens of chloritised milarite crystals on orthoclase have been found in an outcrop of gneiss, with individual crystals to 4.5 cm (Minrec 35.5.410).

At Laperwitzgraben, Kals am Großglockner, Lienz District, Tyrol, Austria milarite crystals to 2 cm have been found with albite variety pericline (Minrec 35.5.410).

At the Jaguaraçu pegmatite, Jaguaraçu, Minas Gerais, Brazil, milarite crystals to 3 cm have been found in vugs in albite (Minrec 35.5.408).

At Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Quebec, Canada, milarite occurs on pectolite crystals in marble xenoliths (Dana).

At the Chardonnet Peak, Mont Blanc massif, Haute-Savoie, France, milarite crystals to 3 mm occur on pink fluorite crystals (Minrec 35.5.408).

At Tittling, Passau District, Lower Bavaria, Bavaria, Germany, crystals of milarite to 5 mm, formed from the alteration of beryl, have been found with rosettes of bavenite crystals and bavenite pseudomorphs after beryl, associated with quartz, albite and chlorite AM 76.1836-1856, Minrec 35.5.408).

At Oberfrauenwald, Waldkirchen, Lower Bavaria, Bavaria, Germany, milarite crystals to 2 mm occur with quartz, bavenite and moraesite (Minrec 35.5.408).

At the Himmelleiten quarry, Roßbach, Wald, Cham, Upper Palatinate, Bavaria, Germany, milarite crystals to 0.5 mm occur in aggregates of fibrous bavenite crystals (Minrec 35.5.408).

Near Henneberg, Weitisberga, Wurzbach, Saale-Orla District, Thuringia, Germany, microcrystals of milarite occur with beryl (Minrec 35.5.408).

At Tanno, Chiavenna, Sondrio Province, Lombardy, Italy, a druse of microcrystals of milarite and bavenite on feldspar has been found (Minrec 35.5.408).

At Monte Cervandone area, Devero Alp, Baceno, Verbano-Cusio-Ossola Province, Piedmont, Italy, milarite crystals to 2 mm have been found on gneiss with muscovite, stilbite, quartz, titanite and hematite (Minrec 35.5.408).

At Val di Crana, Toceno, Verbano-Cusio-Ossola Province, Piedmont, Italy, a single specimen has been found with milarite crystals to 1 mm on albite with bavenite, quartz, fluorite and spessartine (Minrec 35.5.408).

At Vento Valley, Prettau, Puster Valley District, South Tyrol, Trentino-Alto Adige, Italy, milarite crystals to 5.5 cm have been found in a cleft in a band of aplite in amphibolite gneiss, associated with calcite, orthoclase and smoky quartz, or as floaters to 3.5 cm (Minrec 35.5.408-410).

At Tanakamiyama, Otsu City, Shiga Prefecture, Kinki Region, Honshu Island, Japan, prisms of milarite to 1 mm long are found in a pegmatite associated with microcline, schorl, and quartz (R&M.6.525).

At the Kent Massif, Karkaraly, Karaganda Region, Kazakhstan, crystals of smoky quartz have been found with inclusions of milarite to 2 cm (Minrec 35.5.408).

At the Valenciana mine, Guanajuato, Guanajuato Municipality, Guanajuato, Mexico, crystals of milarite to 18 mm occur as aggregates of prisms associated with K-feldspar variety adularia and minor quartz AM 76.1836-1856), and as crystals to 3 cm intimately intergrown with orthoclase with tiny quartz crystals grown on the prism faces of the milarite (Minrec 35.5.407).

At Klein Spitzkopje granite stock, Spitzkopje Area, Karibib, Erongo Region, Namibia, in uranium-enriched syenite, milarite crystals to 2.5 cm occur embedded in calcite and associated with quartz and albite (Minrec 35.5.407-408).

Near Fuglevika, Stavern, Larvik, Vestfold, Norway, milarite crystals to 3 mm occur in syenite pegmatites with microcline, albite and aegirine (Minrec 35.5.408).

At the Himberg quarry, Ramnes, Re, Vestfold, Norway, milarite crystals to 7mm occure in miarolytic cavities in syenite (Minrec 35.5.408).

At the Ermakovskoe Be Deposit, Kizhinginsky District, Buriatia Republic, Zabaykalsky Krai, Russia, milarite crystals to 4 cm occur with bavenite (Minrec 35.5.408).

At Vorderer Zinggenstock, Zinggenstöcke, Oberaar lake area, Grimsel area, Hasli Valley, Bern, Switzerland, fine milarite crystals to 2 cm with orthoclase and smoky quartz (Minrec 35.5.412).

At the Cristallina Valley, Val Medel, Medel, Surselva Region, Grisons, Switzerland, milarite occurs with orthoclase, smoky quartz and apatite (Minrec 35.5.411).

The type locality is the Giuv Valley, Tujetsch, Surselva Region, Grisons, Switzerland, has yielded some of the finest specimens of milarite in the world; it occurs on a syenite matrix together with orthoclase, apatite, smoky quartz and a little actinolite (Minrec 35.5.415).

At Göscheneralp, Göschenen Valley, Göschenen, Reuss Valley, Uri, Switzerland; milarite occurs sparingly with quartz, fluorite and calcite (Minrec 35.5.411).

At the Gischi glacier, Binn, Goms, Valais, Switzerland, milarite crystals to 4 mm occur with pink fluorite (Minrec 35.5.411).

At Fieschertal, Goms, Valais, Switzerland, milarite is associated with orthoclase, epidote, hematite and aggregates of fibrous bavenite. The largest known crystal of milarite, 9.2 cm long, was collected here (Minrec 35.5.413).

At the Foote Lithium Company mine, Kings Mountain Mining District, Cleveland county, North Carolina, USA, milarite crystals to 3mm are associated with albite (Minrec 35.5.407).

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