Planggenstock
46.6306° N, 8.4733° E · ± 1 km
Rock crystal and Smoky quartz from Uri, Switzerland, with photos of specimens from this locality.
Minerals found here
Rock crystal at Planggenstock
Exceptionally clear, very large Alpine-cleft crystals, accompanied by pink fluorite.
- Formula
- SiO₂
- Morphology
- Large crystals and crystal groups grown in an Alpine cleft
- Typical size
- Crystal groups up to 300 kg; the central crystal of the 2005 find is 107 cm long
- Color / luster
- Clear; crystals from the cleft floor can show greenish, cloudy patches from chlorite grains
- Associated minerals
- Smoky quartzfluorite (pink)chloriteadularia
- History
- Opened on 21 September 2005 after eleven years of exploratory digging; the find was bought by the Natural History Museum Bern in 2010 and has been on show there since 2011. The crystals later inspired modern gem-carving artworks.
Smoky quartz at Planggenstock
Giant Alpine-cleft quartz in which smoky and clear crystals occur together with pink fluorite, grown in Aar Massif granite.
- Formula
- SiO₂
- Morphology
- Large crystals and crystal groups grown in an Alpine cleft
- Color / luster
- Smoky shade varies by crystal, depending on how long it was in contact with the radioactive granite; cleft-floor crystals can carry greenish, cloudy chlorite patches while ceiling-side crystals stayed clear
- Associated minerals
- Rock crystalfluorite (pink, up to about 8 cm)chloriteadularia
- Trace elements
- Aluminium-related colour centres produced by natural irradiation (general for the variety, not locality-specific)
- History
- Exploratory digging began in 1994; on 21 September 2005 almost fifty large clear crystals and clusters were found, with another significant find in May 2008. The Natural History Museum Bern bought the 2005 find in 2010 for 4.5 million francs and has shown it since May 2011.
Geology of the locality
- Setting
- Alpine fissure (cleft) formed during the Alpine orogeny about 50 million years ago; hot mineral-rich fluid above 300 degrees C deposited quartz as the rock rose and cooled. The cleft explored by the miners lies at about 2,600 m on the peak.
- Host rock
- Granite of the Aar Massif
- Region
- Uri
- Country
- Switzerland
Coordinates (converted from 46 37 50 N, 8 28 24 E) are those of the peak on the Mindat locality page; the cleft sits below the summit, so the pin is approximate. Permission from landowners and mineral-rights holders is needed before visiting any such site.
Sources
- SRC-132 · Database
Planggenstock, Goescheneralp, Goeschenen Valley, Uri, SwitzerlandMindat.org contributors · Mindat.org - SRC-133 · Museum / collection
Info brochure: The Planggenstock treasure (EN)Natural History Museum Bern · Naturhistorisches Museum Bern - SRC-134 · Article
Quartz crystals from alpine fissures: their formation and the historical significance of alpine quartz as raw material for objets d'artHuegi, M.F. · 2023 · 37th International Geological Congress (IGC), Tokyo
Draft data from the Provenite workbook. Check entries against the cited sources before relying on them. Photos are open-licence images from Wikimedia Commons; the author and licence are given with each photo.