RARE Cassiterite After Orthoclase Pseudomorph Cornwall UK Kohnen Collection For Sale

3.5 cm x 1.5 cm x 1 cmRARE HISTORIC CASSITERITE AFTER ORTHOCLASE PSEUDOMORPH — CORNWALL, ENGLANDEx. Thomas M. Kohnen CollectionAn exceptional historic Cornish pseudomorph featuring cassiterite (SnO₂) after orthoclase feldspar (KAlSi₃O₈), originating from the renowned Thomas M. Kohnen mineral collection.This fascinating specimen displays a sharply defined, elongated crystal form with distinctive angular terminations and a smaller attached crystal projection. Its dark brown to nearly black coloration and finely granular surface are characteristic of classic Cornish cassiterite pseudomorphs.Historic Significance — The Famous 1828 DiscoveryCassiterite pseudomorphs after orthoclase are among the most historically significant and sought-after pseudomorphs from Cornwall, England.The most famous occurrence was discovered at Wheal Coates, St. Agnes, in 1828, when an extraordinary concentration of these unusual pseudomorphs was encountered.This historic discovery was subsequently documented by Stephen Davey in 1832 in the Transactions of the Royal Geological Society of Cornwall.The specimens became celebrated examples of mineral replacement, preserving the original crystal morphology of orthoclase feldspar.Material from this historic occurrence is now highly collectible, with specimens appearing infrequently on the mineral market.Specimen DetailsMineral: Cassiterite after Orthoclase (Pseudomorph)Chemical Composition: SnO₂ after KAlSi₃O₈Locality: Penryn Granite Quarry, Cornwall, England, United Kingdom (per original collection label)Provenance: Thomas M. Kohnen CollectionCrystal Habit: Elongated, angular feldspar crystal form with a secondary crystal projection.Color: Dark brown to nearly black.Luster: Fine granular to subtly metallic.Condition: Please examine all photographs carefully for the specimen’s natural characteristics and condition.Collection ProvenanceThis specimen originates from the Thomas M. Kohnen Collection, an extensive historical mineral collection assembled over decades.The specimen is accompanied by its original collection label identifying it as cassiterite after orthoclase from Penryn Granite Quarry, Cornwall, Great Britain.The original label will accompany the specimen to preserve its documented provenance.A Historic Mineralogical TreasureRepresenting one of the most fascinating mineral replacement phenomena, cassiterite after orthoclase is a classic addition to any serious pseudomorph, British mineral, or historical mineral collection.Its distinctive morphology, historic locality attribution, and documented Kohnen Collection provenance make this an especially interesting collector specimen.You will receive the exact specimen pictured, together with its accompanying collection label.