Surviving early-twentieth-century mine headframe at the closed Förby limestone quarry in Särkisalo, part of a nationally significant cultural environment.
Förbyn vanha kaivostorni is the preserved winding tower of the former Förby limestone mine, located at Isoluoto in Särkisalo, within the present-day municipality of Salo in southwest Finland. The mine was established in 1882 by sea captain Karl Teodor Forsström and remained in operation under Karl Forsström Ab until it closed in winter 2010, making it one of Finland's longest-lived mines at approximately 128 years. The deposit had been worked on a small scale since at least medieval times, with a reference to lime extraction at Krakanäs in 1329.
Industrial open-pit extraction began in 1882 followed by underground mining from 1904 onwards, reaching a maximum depth of 530 metres below surface. The headframe of shaft 1 (kaivoskuilu 1, KK1), completed in 1937, survives on site. Total ore extracted over the mine's history was approximately 9.5 million tonnes.
The Förby mine and its lime quarries are included within the Turunmaan rannikon kalkkilouhokset ja Paraisten kalkkitehdas RKY designation (Museovirasto, 2009).
Lime extraction in the Särkisalo area has medieval origins; the Krakanäs lime quarry is mentioned in connection with Turku Cathedral in a document dated 1329, and quarrying of various kinds continued on the island from at least the seventeenth century. Industrial exploitation began in 1882 when sea captain Karl Teodor Forsström (1850–1912) established Förby Kalkbruksbolaget with 27 initial shareholders. Forsström quickly bought out all partners and proceeded to develop industrial lime production at Förby, building a crusher and transport infrastructure.
The deposit, approximately 600 metres in length, was identified as a particularly pure and fine-grained calcite marble, described as among the whitest and purest known in Fennoscandia. Initial extraction was from open-pit workings using basic methods, with ore transported in wagons for burning. Underground mining began from 1904, and the deepening of the workings over subsequent decades brought the mine to a maximum depth of 530 metres.
Karl Forsström was also instrumental in founding the Lohjan Kalkkitehdas Oy in 1897, and in his later years developed a significant forestry enterprise on the Pettu islands. After his death in 1912 his sons continued the enterprise. The company's activities extended beyond mining to include a processing plant, an electrical workshop, a mechanical workshop, shipbuilding, maritime transport using tugs and barges, farming, and forestry.
A notable vessel, the ice-breaking tug Förby, was built at the site in 1910. The winding tower for shaft 1 (kaivoskuilu 1, KK1) was completed in 1937 and served until the 1950s, lifting stone from the +107-metre level. The associated winding house contained the hoisting machinery, a site office, and a compressed air centre; the tower head incorporated screens that sorted extracted stone into six size categories.
Shaft 3 (kaivoskuilu 3) had an inclination of 52 degrees. In 1928 a fatal underground accident killed four workers who were quarrying at 60 metres depth when a slab of rock approximately three metres long fell from the tunnel roof. In 1981 Karl Forsström Ab and Swiss company Pluess-Staufer AG formed a joint venture, Oy Förby Ab, to handle surface processing of limestone while underground extraction remained with Karl Forsström Ab.
A serious surface collapse occurred on 11 December 1982: a subsidence approximately 100 metres in diameter and several tens of metres deep appeared, engulfing part of the Förby road and tearing off the end wall of a co-operative shop building. The collapse reached to over 200 metres depth and was attributed to fractured rock and over-extraction in the upper levels of the older workings. The affected area remains fenced due to continuing collapse risk.
A smaller collapse had occurred in the upper mine before the Second World War. In its final years the mine employed seven people, with the deepest working level at 530 metres. The mine was closed in winter 2010 because quarrying at greater depths would have been uneconomical; total ore extracted over the mine's history was approximately 9.5 million tonnes.
After closure, the former processing site continued to be used by Omya Oy, an international company processing imported limestone for the paper, cosmetics, glass, and ceramics industries, though Omya subsequently announced plans to close its Särkisalo operations by the end of 2021. The former quarry area has also been used as a storage area. The 1937 headframe survives, though observers note it has deteriorated.
The geocaching community records the nostolaitos as dating from 1936 (a slight discrepancy with the 1937 date given by the company and other sources). In 2009 Museovirasto included the Förby lime quarry and factory within the valtakunnallisesti merkittävät rakennetut kulttuuriympäristöt (RKY) designation Turunmaan rannikon kalkkilouhokset ja Paraisten kalkkitehdas, recognising the surviving steep-sided open-cast workings and the headframe.