gem miningWhere the pay gravel is in superficial soil layers within a few feet from the surface, as for example in dry 'deniyas' or in the bottom slopes of relatively high undulating ground, the land is worked by open cast mining (quarrying) after the removal of any vegetation. The gravel which is rarely thick or extensive in such occurrences is excavated and washed in running water in a nearby stream or in improvised sluices resulting in the removal of the light materials such as sands and clays leaving the heavy residues from which the gemstone material is handpicked by the experienced miner.

Where the overburden of sands and clays is thick and the gravels occur at some depth, the commonest method of extraction is by sinking pits. Their depth varies with the depth of the gravels from five to twenty meters and more. The shaft is divided into two chambers by a partition in the centre, one for excavating and bringing up the gravel from the bottom and the other for dewatering the sump. When the gravel from one chamber is excavated completely, it is then used for de-watering and excavation of the gravel commences in the other chamber. The sides of the shaft are propped up with rough logs or planks to prevent caving in of the loose soft strata. The illam is brought up in baskets by relays of workers until a fair sized dump is accumulated at the pit-head; it is usually covered with bracken. De-watering is commonly by the use of buckets, though some of the larger pits use pumps for this purpose. When the gravel has been completely excavated, mining is stopped and washing of the gravels commences. The gravel is washed in large, shallow wicker baskets in a nearby water course such as a channel or  in a small pond made artificially. At each turn of the basket, a portion of the rim is depressed below the water surface and in the same movement some of the light materials such as clay and sand are swept over the rim by centrifugal  force. Experienced miners show a high degree of skill in washing and succeed in removing all the light material leaving only any gemstone material  present as well as other heavy minerals such  as  limonite.