Evaluation of Natural Defects in Commercial Decorative Rock Deposits in Karnataka, India

Karnataka state is a pioneer in the exploitation of commercial decorative rock resources and in establishing a firm base for the stone industry. The commercial stone industry in the state has grown in status contributing about 40% of the decorative/dimensional stones of both polished and rough blocks exported from the country. Karnataka state forms a part of the Indian Peninsular Shield and extends over an area of 1, 91, 792 km2. Peninsular gneisses, Closepet granite and Younger dykes such as dolerite, felsite and pyroxenite of different ages are the main sources of commercial rock deposits. The state also produces premium varieties like ruby red and black (dolerite) granite and other popular varieties. The demand for the premium varieties is generally steady in international market. World famous commercial ornamental stone varieties are being exploited from Kanakapura, Bangalore, Malaikaval, Hassan, Sira, Tumkur and Illkal in Bijapur districts of Karnataka. Important commercial stones in the Karnataka stone industry are marketed with commercial names such as Imperial red, Himalayan blue, Ocean white, Sabal black, Ruby red, Hassan green, Sawan rose, Sira grey, English teak, Tigerʹs skin, Pink panther, Salt and pepper, Catʹs eye, and Chilly red. ccess of the commercial stone industry solely depends upon the availability of large reserves of defect free rock deposits. Detection of defects in commercial rock deposits plays an important role in quality assessment. Macro defects can be detected by visual examination of commercial rock deposits. Micro discontinuities such as altered or twisted minerals can be detected by systematic micropetrographic analysis of the rock specimens. In Karnataka, too many organizations, entrepreneurs and individuals are investing huge amounts without evaluating the quality of the deposit. This results in poor quality stone and subsequent quarry abandonment. Quarry owners and stone exporters should be quality conscious about export-oriented natural stones in order to remain in the business and maintain the reputation of the Karnataka stone industry.