Shatter Cones

Sierra Madera Shatter Cone - 457g. 457 grams. Approximate size: 6.0" x 3.2" x 1.0". Location: Sierra Madera Crater, Pecos County, Texas. Well-defined striae on both sides. Side one features fine radiating horsetail patterns and the outline of a Permian brachiopod fossil; side two features coarser striae. This is a shatter cone specimen in Permian limestone from the Sierra Madera Crater in Pecos County, Texas. Shatter cones are rare impact-related structures with distinctive cone-shaped fractures and grooved, radiating striae that form under extreme shock pressure from hypervelocity meteorite impacts. The discovery of shatter cones, impact breccia, and shocked quartz in the 1960s helped confirm Sierra Madera as an impact structure. The crater formed about 100 million years ago and is an 8-10 mile-wide complex impact structure with a central uplift containing folded and faulted carbonate and siliciclastic rocks.