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In Lundeborg, you will find two former raw material extraction areas.

Grønneskov and Knarreborg Watermill. In Grønneskov, diatomite (see later) and the characteristic 'White Sand' were extracted in the past, known from several locations in Southeastern Funen and especially in the Archipelago, where it appears in many cliffs.

The sand consists of 96 percent pure quartz, the world's most common mineral.

The lower parts were primarily deposited by running water, while in the upper parts of the sand, it is primarily wind-deposited.

The sand is believed to have been deposited in an Arctic environment prior to the so-called Ristinge Advance 50-55,000 years ago in the middle of the Weichselian Glaciation. In the sand, traces of permafrost are found locally, including in the form of fossil ice wedge and frost crack structures and so-called cryoturbation structures (popularly called kettle soil, after the kettle, bowl, or sack-shaped structures).