Galena diode. Making such wireless receivers was a popular home hobby in Britain and other European countries during the 1930s. Scientists associated with the investigation of the diode effect are Karl Ferdinand Braun and Jagadish Bose. In modern wireless communication systems, galena detectors have been replaced by more reliable semiconductor devices. Galena Galena, also called lead glance, is the natural mineral form of lead(II) sulfide. It is the most important ore of lead and an important source of silver. Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral
National Mineral Development Corporation National Mineral Development Corporation </nowiki> NMDC Limited, previously known as National Mineral Development Corporation, is an Indian state-controlled mineral producer. It is 72.43% owned by the Government of India, under the administrative control of the Ministry of Steel. It is involved in the exploration of iron ore, copper, rock phosphate, limestone, dolomite, gypsum, bentonite, magnesite, diamond, tin, tungsten, graphite etc. It is India's largest iron ore producer and exporter producing more than 35 million tons of iron ore from 3 fully mechanized mines in Chhattisgarh and Karnataka. It also operates the only mechanized diamond mine in the country at Panna