Hi, I don't know about gravity for this grit separation, but the gold maybe. Although the gold and silver grains are very fine, gravity concentration may also have an application for recovering free gold from carbon fines, and research on this application is warranted. 

In a paper http://www.onemine.org/document/document.cfm?docid=8756 you can review and learn that  if you try flotation tests in a 2-L Denver flotation cell to recover gold and carbon.  Pulp density in the flotation cell to about 15% solids (by weight).  Because the carbon fines have been collected after the stripping circuit and the finer carbon could have a more effective stripping, the existence of fine gold grains could be the predominant factor. For this reason, sodium diisobutyl dithiophosphate can be added as one of the collectors for a better flotation of free gold. 

A relatively straightforward flotation sequence of three stages of gold flotation and two stages of carbon flotation can be adopted. Each subsequent stage of flotation could be conducted on the tailings from the previous stage.

Pine oil, is added in the first-stage carbon flotation, but not in the second stage carbon flotation as it shows a detrimental effect on carbon flotation. This is contrary to a typical coal flotation process where pine oil is a very popular frother.  Compared to pine oil, MIBC seems to be less detrimental to carbon flotation, but also less effective for gold flotation. 

Carbon fines materials are usually produced in gold mining operations when carbon adsorption processes are used to recover gold. Gold grades in the carbon fines materials vary from 0.17 to 0.68 kg/t (5.0-19.9 oz/st) at the Fort Knox Mine. The sample used in this study contained about 0.27 kg/t (7.9 oz/st) of gold. Test work and analyses revealed the presence of free gold grains in the carbon fines. Flotation analyses showed that about 80% of the gold values are in the form of free gold while 20% are in the form of adsorbed gold on the carbon. More than 95% of gold and 90% of carbon can be recovered by three stages of gold flotation followed by two stages of carbon flotation. Gravity concentration may also have an application for recovering free gold from carbon fines.

Shaking tables are an excellent method of separating coarse and fine sands from carbon.  We treat small amounts of carbon, so we use an RP-4 table, but I imagine any Wilfley/Deister type table would work.

The bulk of the carbon reports to the tailings port.  Be sure and screen your middlings port as sometimes carbon reports there as well.  If this is the case, simply pass this material over the table once more.  

A good table operator can recover up to 90% of the carbon as a clean product on the first pass.  I hope this helps.

Using spirals to separate carbon from sand works well but can be a slow process depending on the amount of carbon to be treated. Used spiral banks can be purchased relatively cheap and take up a small footprint if space is a limiting factor.

is there any literature review on gold recovery from grits? if any please can i get one which is the best

The best method, which I have used, is a Denver-type jig. Works a treat!!