SMOKY GWINDELS ON ADULARIA
ABOUT THE SPECIMEN
Five main crystals of fine smoky quartz, surrounded by smaller crystals of quartz and adularia, all atop a very attractive alpine feldspar matrix that's been well-trimmed for maximum display value. Best of all, the grouping features an excellent pairing of two gwindels intergrown with one another. The dominant gwindel, measuring over 4 cm, is a textbook example of the highly coveted ‘sucre’ (closed) morphology, while its companion displays a prismatic, or open habit. Such matrix-anchored gwindels are scarce, so to have two of them intergrown on a gorgeous adularia-dominant matrix makes for a wonderful rarity. The color of the crystals is deep and rich, the luster like a mirror, and the clarity is water-clear. Surrounding the smokies at the base, the layer of adularia appears like a sheet of snow that adds an elegant contrast. What appears to be chipping on the larger gwindel isn't damage, rather a result of the gwindel growth process; there's only minor chipping towards the periphery. Considering the combination of color, contrast, habit, and locale, this really is a top-notch alpine specimen. Ex Evan Jones.
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The Cavradi Gorge cuts through the Aar Massif and Tavetscher Zwischenmassiv - Variscan crystalline basement rocks subjected to Alpine metamorphism - exposing a concentration of open fissures that rank it among the most mineralogically productive alpine localities in Switzerland. Gwindels form in a temperature window between roughly 300-450°C as quartz grows elongated along an a-axis rather than the c-axis typical of normal prismatic crystals; Cordier and Heidelbach's 2013 TEM study confirmed the twist results from a high density of straight screw dislocations inducing an Eshelby twist - spiral growth under exceptionally low supersaturation rather than any external mechanical deformation. Tschermak's still-current 1894 morphological classification distinguishes open, half-closed, and closed forms depending on how completely the rhombohedral faces envelop the central axis. Cavradi gwindels are predominantly smoky, with colorless examples considerably rarer; matrix specimens are unusual given the narrow fissure geometry. The gorge also produces iron roses with rutile overgrowths, anatase, and dravite - a suite covered in Hager et al.'s 2013 German-English monograph devoted entirely to the locality. Active recovery requires rope work above a wildly rugged ravine, and local regulations restrict blasting to community residents - constraints that keep supply genuinely limited relative to the locality's fame.