Adularia ('fourling' twins) (4 piece set) (ex Kay Robertson Collection)

Item Description

A beautiful and diverse set of the classic and highly desirable Adularia "fourling" twins from the famous Cavradischlucht in Switzerland. This locality is world famous for its magnificent Hematite specimens often associated with blood red epitaxial Rutile. The "fourling" twins of Adularia are fairly rare from this locale (and from the Europeans Alps in general), so to have a set like this a big deal. The pieces are all very well-formed, showing the rarely seen twinning habit comprising (ideally) four crystals with a compressed pseudo-rhombohedral form {110} in the Manebach habit intergrown to create an almost "flower"-like formation. As you can see from the specimens in this set, sometimes additional crystals join the party, creating additional twinning planes with a more complex form. The four specimens in this set range from virtually colorless / white to a silky silvery-grey hue to a reddish-pink tone (caused most likely from either clay or iron content). They are all well-formed and complete with no major damage, but a few nicks can be seen here and there. The luster ranges from glistening to matte, and the clarity is virtually WATER CLEAR in some areas to milky / translucent in others. If you're a fan of Feldspars, Alpine minerals, twinned minerals or just interesting mineral morphology, do not miss out on this attractive set that ranges in size from 2.2 x 2.0 x 1.7 cm to 3.7 x 2.7 x 2.5 cm. Valued in the inventory at $1,000 together. It should be noted that Adularia used to be defined as a variety of Orthoclase, but mindat.org defines it as an "ordered low-temperature variety of Orthoclase or partially disordered Microcline". Ex Kay Robertson Collection (#11907 a, b, d, & e - "c" was not present when we acquired the collection). Kay is a prominent California collector, who specialized in European classics (see the article in the March-April, 2007 Mineralogical Record and the 50+ page article in the German Magazine "Mineralien Welt" November-December 2017).