{"title":"Leucite","description":"\u003cp\u003e\u003cstrong\u003eLeucite\u003c\/strong\u003e (KAlSi₂O₆) is a potassium aluminum silicate placed by petrologists in the \u003cstrong\u003efeldspathoid group\u003c\/strong\u003e, alongside \u003cstrong\u003enepheline\u003c\/strong\u003e, \u003cstrong\u003esodalite\u003c\/strong\u003e, \u003cstrong\u003ehauyne\u003c\/strong\u003e and \u003cstrong\u003elazurite\u003c\/strong\u003e. Feldspathoids are minerals with chemistries near those of the alkali feldspars but poor in silica content. Leucite crystallises with a cubic structure at high temperature around 900°C, but upon cooling to 700-600°C it transforms into a tetragonal modification stable at room temperature, forming characteristic polysynthetic twin lamellae, a transformation that is reversible. Its most common habit is trapezohedral crystals, though it can also occur granular or as euhedral, pseudo-cubic crystals, and twinning is common though hard to see because of leucite's low birefringence. The name comes from the Greek \"leucos\" for white, describing its typical white-to-grey, vitreous crystals, which register 5.5-6 on the Mohs scale with poor cleavage and conchoidal fracture.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eMount Vesuvius\u003c\/strong\u003e and \u003cstrong\u003eMonte Somma\u003c\/strong\u003e in Campania form the historic type locality, with further fine Italian material from the \u003cstrong\u003eAlban Hills\u003c\/strong\u003e near Rome (Villa Senni, Frascati, Ariccia), \u003cstrong\u003eRoccamonfina\u003c\/strong\u003e, and \u003cstrong\u003eVulcano\u003c\/strong\u003e in the Lipari Islands. Beyond Italy, notable leucite localities include the Laacher See and Eifel district of Germany; the Leucite Hills of Sweetwater County, Wyoming, the Bear Paw Mountains of Montana, and Magnet Cove, Arkansas in the USA; the West Kimberley district of Western Australia; Kilimanjaro in Tanzania; and the Ruwenzori and Kariya areas of Uganda. Mount Nyiragongo in Congo's Kivu Province adds another classic African source. These occurrences are hosted in potassium-rich, silica-undersaturated volcanic rocks such as leucitite, tephrite, and leucite-phonolite, where leucite crystallizes with clinopyroxene, sanidine, and nepheline.\u003c\/p\u003e\u003cp\u003eCollectors prize leucite for its sharp, pseudo-icositetrahedral crystals perched on dark lava matrix, a striking contrast rarely matched among rock-forming silicates. Although abundant in various lava rocks, leucite is extremely rare in gem-quality form and often has a milky or cloudy look, so faceted stones and well-shaped crystals are especially prized by collectors. To date only Italy has produced transparent, facetable leucite, with the Alban Hills near Rome yielding colorless crystals up to about 1 cm. Fine matrix specimens showing the mineral's diagnostic twinning and pseudo-cubic outline, alongside associated \u003cstrong\u003eclinopyroxene\u003c\/strong\u003e, \u003cstrong\u003esanidine\u003c\/strong\u003e and \u003cstrong\u003etitanaugite\u003c\/strong\u003e, remain a benchmark for systematic feldspathoid and Vesuvian mineral collections.\u003c\/p\u003e","products":[{"product_id":"leucite-twinned-trapezohedron-crystals-roccamonfina-italy","title":"LEUCITE – Twinned Trapezohedron Crystals, Roccamonfina, Campania, Italy","description":"\u003cp\u003eA striking leucite specimen showing the classic trapezohedral crystal form, further enriched by well-developed twinned crystals that highlight the aesthetic and mineralogical value of this feldspathoid species from the historic Roccamonfina Volcanic Complex. The overall crystallization quality and balanced habit make this piece a fine representative of Italian volcanic mineralogy.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eMineral Data:\u003c\/strong\u003e\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eDimensions:\u003c\/strong\u003e 120 x 76 x 56 mm\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e 240 g\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eProvenance:\u003c\/strong\u003e Roccamonfina Volcanic Complex, Caserta, Campania, Italy\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"ITALMINERAL","offers":[{"title":"Default Title","offer_id":45737608806509,"sku":null,"price":139.0,"currency_code":"EUR","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0693\/8027\/6333\/files\/IMG20260502223347.jpg?v=1788067432"}],"url":"https:\/\/www.italmineral.com\/collections\/leucite.oembed","provider":"ITALMINERAL","version":"1.0","type":"link"}