Kosov Quarry, Limestone quarry in Jarov, Czech Republic

Kosov Quarry is an abandoned limestone and shale quarry near the settlement of Jarov, about 3.5 km from Beroun railway station in the Český kras protected landscape area. It has seven quarry benches and a strongly elongated north–south lake on its floor. Silurian limestones lie in the upper benches, while shale occurs mainly around the lake.

Kosov Quarry was opened in 1909 by the cement works at Králův Dvůr to supply Silurian limestone and shale as a corrective raw material for cement. Extraction peaked between 1909 and 1941, when a 65 cm narrow-gauge railway, a steam loader and a horse-drawn system fed a cableway to the plant. Mining stopped in 1954 because of unfavourable geology, and the site is now being backfilled.

The quarry's Czech name, Lom Kosov, comes from the nearby settlement of Jarov, and the site is known among fossil collectors for its Silurian cephalopods and prehistoric marine fauna. Visitors can still make out the seven quarry levels, numbered from the top terrace down to the flooded seventh level at the lake.

The quarry is abandoned and closed to the public, and swimming in the lake on its floor is prohibited; the site is gradually being backfilled. It lies in the Český kras protected landscape area, about 3.5 km from Beroun railway station near the Jarov settlement. The operator is Velkolom Čertovy schody, a.s., based in Tmaň.

Fossils of ancient sea creatures have been found in the stone layers at Kosov, pointing to a time when this part of the Czech Republic was covered by a shallow sea. Researchers study these finds to understand how the seafloor in this region changed over millions of years.