This is a large teardrop-shaped Tektite from Thailand.
Tektites are gravel-sized bodies composed of black, green, brown, or gray natural glass formed from terrestrial debris ejected during meteorite impacts. The term was coined by Austrian geologist Franz Eduard Suess, son of Eduard Suess. They generally range in size from millimetres to centimetres.
This tektite weighs 145g and measures 99 x 36 x 40mm
Thank you for looking
Castle Rocks Cornwall x