There is some coal mining in the area, as well as some (unused) phosphorite reserves.
en.wikipedia.org The area is also rich with mineral resources such as iron ore, tin, gold, copper, diamonds, molybdenum ore, and phosphorite.
en.wikipedia.org Namely, oxygenation brought about important alterations to the sulphur cycle, which provided an environmental niche for sulphur bacteria to create phosphorite beds.
phys.org Minerals that typically form nodules include calcite, chert, apatite (phosphorite), anhydrite, and pyrite.
en.wikipedia.org It's said that phosphate rock is formed in oceans in the form of calcium phosphate, called phosphorite.
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