John’s Stone: A possible fragment of the 1908 Tunguska meteorite

•John’s Stone is a possible fragment of the Tunguska meteorite 1908.•John’s Stone moved with high velocity through the permafrost.•Estimated landing velocity of John’s Stone (550 m/s) exceeded free fall velocity.•Trajectories of John’s Stone landing and Tunguska body flight coincide.•John’s Stone is sedimentary metamorphic quartz-rich conglomerate gravelite sandstone.

The aim of this study was to discover remnants of the 1908 Tunguska meteorite. Field studies identified exotic rocks, furrows, and penetration funnels reported by the first eyewitnesses. Main methods included decoding of aerial survey photographs, systematic survey of epicenter area of the Tunguska explosion, exploratory excavations, reconstruction studies of the exotic rocks, mineralogical and spectral analysis of specimens, and experimental attempt of plasma-induced reproduction of fusion crust. The authors report the discovery of funnel-like structures and of an exotic boulder known as John’s Stone (JS) in the epicentral area. The article provides detailed description of JS, fresh furrows in the permafrost, multiple shear-fractured splinters, splinters with glassy coatings, evidence of high-speed impact of JS in the ground, and clear consistency in the geometry of spacial arrangements of all splinters, furrows, and cleaved pebbles. Pattern of permafrost destruction suggested about high-speed entry and lateral ricochet of JS in the ground with further deceleration and breakage. Calculated landing velocity of JS was at least 547 m/s. John’s Stone is composed of highly silicified gravelite sandstone (98.5% SiO2) with grain size of 0.5–1.5 cm. Outer surface of several splinters showed continuous glassy coating similar to shiny fusion crust reminiscent of freshly applied enamel. Plasma-induced heating of John’s Stone specimen led to its explosive disintegration; residue presented with light-colored semi-transparent pumice-like grains and irregularly shaped fused particles. Overall, our data suggest that John’s Stone may be a fragment of the 1908 Tunguska meteorite and may represent a new type of meteorite.