The resultant magnesite may be very pure. Sedimentary deposits usually occur as thin layers of variable magnesite quality. Lacustrine magnesite deposits consist of nodules of cryptocrystalline magnesite formed in a lake environment. Both vein filling and sedimentary magnesite occurrences are rarely mined on a large scale. The estimated world economic resources of magnesite are about 8600 million tonnes of MgCO 3 .
China is ranked first, followed by the Russia, and North Korea.
The deposit is thought to have formed by the deposition in lakes of magnesium bicarbonate derived from the alteration of serpentinite rock. Evaporation caused hydrated magnesium carbonate to precipitate. Deposition of mud over the magnesite caused further evaporation and the formation of hard nodules of dehydrated magnesite. Mining of this deposit commenced in 1989. Similar magnesite deposits occur at Yaamba and Triple Four, also in the Rockhampton area.