Medium is relative. I bought 2 kilos of meteorites. About 8 grams more or less. About 15mm. Made of nickel, iron and other trace metals. Will make cool earrings if wirewrapped. These meteorites are part of the Campo Del Cielo meteorite. The Campo Del Cielo craters were discovered in 1576 by Spanish explorers in Chaco Argentina. Thousands of meteorite pieces have been found near the impact craters. The largest meteorite found weighs an immense 37 tons. Scientists have estimated the date of the fall to be around 3950-5800 years ago based on radiocarbon dating of charred wood in the vicinity of the craters.