{"title":"Orthoclase","description":"\u003cp\u003e\u003cstrong\u003eOrthoclase\u003c\/strong\u003e is a potassium-rich member of the alkali \u003cstrong\u003efeldspar group\u003c\/strong\u003e, chemically KAlSi3O8, and one of the most important rock-forming minerals in the Earth's crust. It is the most common member of the series, being the dominant K-feldspar in most granite, granitic rocks and other plutonic rocks, with an intermediate cooling regime. Structurally it sits between disordered monoclinic \u003cstrong\u003esanidine\u003c\/strong\u003e and fully ordered triclinic \u003cstrong\u003emicrocline\u003c\/strong\u003e, sharing the same composition as the latter but stable at higher temperature. Orthoclase got its name because it has two directions of cleavage, which are at right angles to one another, a diagnostic feature collectors use alongside its typical prismatic, often twinned habit — Carlsbad, Baveno, and Manebach twin laws are all named after classic orthoclase occurrences.\u003c\/p\u003e\u003cp\u003eTypical crystallized orthoclase comes from granite and pegmatite localities across the Alps and beyond: \u003cstrong\u003eSt. Gotthard\u003c\/strong\u003e and \u003cstrong\u003eVal Giuv\u003c\/strong\u003e in Switzerland, the \u003cstrong\u003eZillertal\u003c\/strong\u003e in Austria, and in Italy the historic twin locality of \u003cstrong\u003eBaveno\u003c\/strong\u003e in Piedmont together with \u003cstrong\u003eSan Piero in Campo\u003c\/strong\u003e on Elba. Classic twinned forms come from Carlsbad in Czechoslovakia, and well-formed red crystals from Kirkpatrick in Scotland, Flims in Switzerland, Marienburg in Germany, and Striegau in Silesia. Fine adularia-type orthoclase from alpine clefts is also prized, with exceptional crystals from \u003cstrong\u003eHabachtal\u003c\/strong\u003e in Tyrol. In the United States, notable material comes from the \u003cstrong\u003ePala\u003c\/strong\u003e and \u003cstrong\u003eMesa Grande\u003c\/strong\u003e pegmatite districts of San Diego County, California, and from Oxford County, Maine.\u003c\/p\u003e\u003cp\u003eThe finest gem-quality orthoclase, however, is the transparent yellow variety from \u003cstrong\u003eMadagascar\u003c\/strong\u003e, especially the \u003cstrong\u003eItrongay\u003c\/strong\u003e (Itrongahy) and \u003cstrong\u003eAmpandrandava\u003c\/strong\u003e pegmatites near Betroka in Fianarantsoa Province. Crystals from Itrongahy are very fine, transparent yellow and very large, up to 250 carats, making Madagascar the world's leading source of cuttable orthoclase. Related gem varieties include \u003cstrong\u003emoonstone\u003c\/strong\u003e, the schiller-effect orthoclase-albite perthite valued in jewelry, with fine material from Sri Lanka, Myanmar, Brazil, and India. Collectors seek orthoclase for its sharp twinned crystal forms, its role as a type example of feldspar structural states, and the rarity of genuinely gemmy, transparent specimens set against the mineral's ubiquity as a common rock-former.\u003c\/p\u003e","products":[{"product_id":"smoky-quartz-pink-orthoclase-baveno-italy","title":"SMOKY QUARTZ \u0026 PINK ORTHOCLASE – Striking Color Contrast, Baveno, Italy","description":"\u003cp\u003eA delightful miniature specimen combining a lustrous Smoky Quartz crystal with vividly pink Orthoclase feldspar, from the world-famous granite pegmatite pockets of Mount Camoscio at Baveno. The deep grey-brown of the quartz creates a striking visual contrast against the salmon-pink feldspar matrix, a color pairing that has made this Italian locality legendary among collectors and the type area for the classic 'Baveno law' feldspar twinning.\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 29 x 28 x 15 mm\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e 9.22 g\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eProvenance:\u003c\/strong\u003e Seula mine, Mount Camoscio, Oltrefiume, Baveno, Verbano-Cusio-Ossola Province, Piedmont, Italy\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"ITALMINERAL","offers":[{"title":"Default Title","offer_id":45732501618797,"sku":null,"price":9.0,"currency_code":"EUR","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0693\/8027\/6333\/files\/AGC_20240801_182133461.jpg?v=1787996721"},{"product_id":"orthoclase-smoky-quartz-monte-maria-sardinia","title":"ORTHOCLASE \u0026 SMOKY QUARTZ – Pink Crystal Contrast, Monte Maria, Sardinia, Italy","description":"\u003cp\u003eA striking natural intergrowth of a pink Orthoclase crystal set within a lustrous Smoky Quartz crystal, both fully developed and well terminated. The vivid pink-to-smoky brown color contrast, combined with clean crystal faces on both individuals, makes this a distinctive specimen from a Sardinian locality prized for this exact mineral association.\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 83 x 62 x 37 mm\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e 197 g\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eProvenance:\u003c\/strong\u003e Monte Maria, Domus de Maria, South Sardinia, Sardinia, Italy\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"ITALMINERAL","offers":[{"title":"Default Title","offer_id":45733359845485,"sku":null,"price":159.0,"currency_code":"EUR","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0693\/8027\/6333\/files\/AGC_20250317_225131065.jpg?v=1788004405"}],"url":"https:\/\/www.italmineral.com\/collections\/orthoclase.oembed","provider":"ITALMINERAL","version":"1.0","type":"link"}