Rajoany and other local people say that the operation uses mercury to separate gold from other material in ore — a hazardous technique that is common in the Global South but that has not historically been used in Madagascar.
Centrifuges method This method employs a simple vessel that rotates against a central point to separate the heavier gold from the lighter materials within the ore. A centrifuges vessel works by separating various materials by their density. When using this method you pour your crushed gold ore into the vessel using a pipe at the top of the vessel.
Gravity separation is an ancient and the most commonly used gold enrichment method. Placer gold is usually showed a single native gold in the form whose particle size is generally greater than 16 t/m3 having big density contrast with gangue. So the gravity separation is the most important method for placer gold beneficiation.
In Benguet province a group of miners have been using the mercury-free gravity-borax method (GBM) for gold extraction for decades. This method basically requires the same equipment as the amalgamation methods.
Electroparting is recent gold refining procedure where gold is separated from other metals in electrolytic cell in a way that dissolves all metals except gold and platinum. This procedure refines gold directly producing up to 99.5% purity gold powder in a single step. AcidLess vacuum distillation process
The free gold that remains undissolved is separated by means of gravity separation methods. After gravity separation additional comminution is carried out after which the sulphide minerals are decomposed and the gold-containing solution or residue is routed to the concentrate leaching circuit.
Because of the large proportion of gold gravity separation process is the most common method of recovering gold and is often used in combination with other gold separation methods to treat all kinds of gold ores especially the alluvial gold mine.