Most (but not all) orthoclase crystals have plagioclase rims (type Vyborgite, named after the city of Vyborg)
The rocks that break off the Rotes Kliff - such as flint, rhomb porphyry or Rapakivi granite - still enable an accurate determination of their origin to be made.
granite | Granite | Granite Falls | The Granite Club | Seven Blocks of Granite | Granite Falls, North Carolina | Granite Falls, Minnesota | Granite Belt | Rapakivi granite | Granite Railway | Granite, Iowa | Granite Hills | Granite County, Montana | Granite County | Granite Construction | Granite Broadcasting Corporation | Granite Bay, California | Granite Bay | 20 Granite Creek |