Gold deposits not ruled out by geologists
PANJIM, AUG 1
Iron ore, manganese and bauxite may be the main minerals of Goa but it has been revealed that there are occurrences of quartzite, platinum, rhodium, chromite and soapstone in the State and the good news is that geologists do not rule out deposits of gold, ilmenite and monazite in some pockets of the State.
During geological investigations carried out by the Geological Survey of India (GSI), occurrences of quartzite deposits have been revealed, says an official document of the Department of Mines.
The geological investigation was conducted over an area of 20 square kilometers around the villages of Concem and Shiroda in Ponda taluka.
Quartzite appears to be suitable for manufacture of coloured glassware, ferrosilicon and refractory bricks. It is hard, massive and almost white in colour. A reserve of 14.5 million tonnes of quartzite is estimated over a depth of just 10 metres.
Chemical analysis revealed 96.18 to 97.64 % silica with 0.84 to 1.06 % iron content in the weathered quartzite while fresh quartzite analysed 97.7 % to 99.4 % silica with 0.15 % to 0.97 % iron.
The preliminary studies have also revealed that there are occurrences of low grade chromite and soapstones too. Presence of soapstone deposits is seen in parts of Sattari and Quepem The report , however, says the occurrence needs to be considered for investigation.
Soapstones are a soft heavy compact variety of talc having a soapy feel and are used to make hearths and tabletops and ornaments.
The residual placer deposits such as those of gold should be actively investigated, the Directorate of Mines report said. It also suggested that a similar approach should be adopted for ilmenite and possibly monazite placers on the continental shelf. Ilmenite is a black-coloured mineral composed of of iron, titanium and oxygen.
It further said that a mafic-ultramafic complex extending over a strike length of 20 km with a maximum width of 4 km has been observed near Usgao in Ponda taluka.
The major constituents include dunite, peridotite, pyroxenite, and gabbro. The ultramatic variants include dunite and harzburgite host chromite mineralization at Bondla and Usgao.
Bondla: Occurrences of platinum, rhodium, iridium, and rhetherneum have been detected by GSI from the chromite samples of Bondla area.
Two chromite bodies occurring within serpentinised dunite have been delineated in the area around 1-2 km east and northeast of Bondla.
Geologically the entire State of Goa is covered by rocks of the Dharward super group of the Archean Proterozoic age except a narrow strip in the north-eastern corner of Goa. The Dharwar super group consists broadly of four formations of which the Bicholim formation commands more weight due to the commercial angle as it contains iron and manganese ore deposits.
Iron & manganese: Iron and manganese ore deposits are reported along a 95-km north west-south east trending belt The larger and better iron ore deposits occur in North Goa between Advalpal and Usgao. There is a gradual decrease in concentration of iron ore and increase in the concentration of manganese towards the south.
The total estimated in situ reserves, tentatively, as per the Indian Bureau of Mines, are of the order of 926 million tonnes.
Tentatively, the estimated in situ reserves as per IBM are of the order of 19 million tonnes.
Generally, bauxite occurs at irregular pockets within a length of around 130 km.
Sizeable occurrences of limestone has been found in the north easern corner of Goa in Sattari taluka.
Minor minerals: The minor minerals available in the State are basalt/granite metal, laterite, rubbles, ordinary sand, brick earth an d lime shells
Off shore: Studies could also be carried out for offshore minerals along the coast of Goa especially for petroleum and manganese nodules. Sources said that the Central government had conducted some explorations around 10 years ago and indications are that deposits of mineral resources were detected.
