Limestone was made on the seabed near the equator in the central part of the Pacific Ocean. It was created by the precipitation of foraminifers, coral reefs, lime algae and such about 300 million years ago, and approached closer to the Asia continent with the plate moving. The ancient Kyushu is said to have been composed of two islands, and the core of the northern island is Hiraodai, and the southern island is the karst of Tsukumi. With ocean in between, the same goes for Akiyoshidai of Yamaguchi prefecture and Nanyo karst of Shikoku region.
The limestone stratum of Tsukumi continues inland for approximately 20 kilometers, which reaches further into Bungo Ono. Many limestone caves are seen, such as Kariu and Onagara in the south of the mountain range, and Furen and Inazumi in the north, as well as various places with “white” in their names such as Hakusan (white mountain) and Shiratani (white valley).
It was during the Edo period when the limestone started to be treated as products. In Usuki Kokagami, they said the Usuki clan placed the Lime Mining Office in 1862, but with the work of Matahei Yakiishi and various other records, it seems the origin of lime burning goes back nearly a century further.
Into the modern days, with the rise of the cement industry, private sectors started the mining in full scale. The limestone in Tsukumi is high in purity, and the superior mine boasts the largest production volume in Japan today. With the estimated deposit amount of 4.5 billion tons, it is expected to continue its lead in the future.