Manganese Nodules


What are m n?


The Cook Islands Exclusive Economic Zone (EEZ) covers 1.8 million square kilometres. In this area, the most significant mineral resource is manganese nodules that are found on the seabed (see cover drawing of a nodule cross-section). These nodules are formed by metallic elements that slowly precipitate out of the ocean water. The most abundant element is manganese. Nodules may grow at a rate of about two millimetres per million years. Deep currents flowing from the Antarctic region towards the equator influence the formation of nodules in Cook Island waters, which are rich in cobalt, nickel and copper.


Manganese Nodules are small, dark, potato-shaped little balls where metals and other minerals have accumulated around a core over a few million years. The core can be a prehistoric shark tooth, a piece of prehistoric whale bone, a meteorite fragment or similar. They contain a relatively high percentage of useful metals, i.e. Nickel, Copper, Cobalt, Manganese and Iron, though the tailings (residues) are approximately 75% of the dry mass. They are mostly found in water depths of 4000-6000 metres in large fields often distant by a few thousend km from the closest continent shores.


There are so many of these nodules on the bottom of the ocean, that the metal reserves associated exceed for many metals the amount of known deposits on land. The difficulty to use them today is mainly of technical nature. Though it is not very difficult to pick them up in little amounts, e.g. with a grab sampler or with a dredge, it is very difficult to mine them in such quantities that they can be processed and the valuable metals extracted and still be competitive with land won metals.


What could the substances obtained from manganese nod be used for?


Cobalt is the most valuable metal in these nodules, worth 10 to 30 times more than copper or nickel; Cook Islands nodules have among the highest cobalt content recorded in the Pacific. It is estimated that the cobalt resource is about 32 million tonnes, enough to sustain the current world demand for 520 years.


Cobalt is utilised in diverse industrial applications, mostly in superalloys used by the aircraft industry. Demand is also increasing for use in rechargeable batteries for laptop computers and other applications.


Since the Manganese Nodules contain so many different types of metals they are very useful. There is a wide range of uses for the metals contained within manganese nodules, for example people can use the metals to make:



o Batteries (non- alloy) which have manganese dioxide
o Catalysts.
o Manganese nodules can also help to recycle glass.
o Steel (consumption of manganese are used during iron production.)
o Fevrites,
o Welding fluxes,
o Agriculture,
o Water treatment,
o Fuel additives,
o Oxidising metal coating,
o Circuit boards,
o Sulphur dioxide removal,
o Hydroquinone production (consumption of manganese ferro-alloys to create steel.) ( Non- ferro alloys crust have iron. 95% used for iron and steel industries to purify iron and make alloys. (strengthens, touchiness, stiffens, resistance, hardens, hardonability, true amethyst.
o Etc.
There is almost no limit to all the uses of manganese nodules. It goes from very important uses as making steel, to smaller less important uses as the production of cutlery.


How are they collected?


Cook Islands nodules occur in very deep waters, on the order of 5,000 metres. These depths pose many challenges, not least of which includes finding an economically viable mining system.


it\'s hard to mine efficiently under 3000 meters of water.


Development of Deep-sea Manganese Nodules


It consists of four different process, i.e. exploration, mining, transportation and metallurgy. Among these, the mining process can be classified as three categories of collecting system, lifting system and mining ship. The collecting system and lifting system are the most important parts in the commercial mining process.




Lifting System


This is the key system to control the success of total mining system in deep-sea mining project and it based on the lifting method is classified as the hydraulic pumping system and the air lifting system of the fluid dredging type, the continuous line buckets system of the mechanical type and the modular marine mining automation system. The fluid dredging type has been extensively studied in U.S.A et al.; the continuous line buckets system in Japan. The modular type is proposed as the