A considerable part of peninsular India, the Indian Shield, consists of Archean gneisses and schists which are the oldest rocks found in India. Around Bombay, on the northwestern side of the peninsula, are covered by the Deccan Trapp, thick layers of basaltic rocks formed by lava flows during the Cretaceous. Along the northern border of India is the Himalaya, so there is a narrow region of alpine mountain ridges which also belongs to the country. The peninsula is connected to the Himalay by a wide plain which is the river course of the Indus in the west and the Ganges in the east.
This are actually quite poor preconditions for the formation of natural caves. River plains are loose sediments and also the groundwater is close to the surface, there is no underground drainage as the river drains the area and so there is no karstification. Metamorphic rocks are mostly crystalline which means insoluble, so there is neither karstification. The Trapp basalt could contain lava tubes, but as it formed more than 60 Million years ago they are long gone, if they existed. What remains are three possibilities: small patches of metamorphic limestone in the shield, the limestones of the southern Himalaya, which includes the most important karst area of India in Meghalaya, and tectonic caves in the metamorphic rocks.
On the other hand there is an enormous amount of artificial caves which were dug during the last 2,000 years into the granite and gneiss. They were hermitages, monasteries and cave temples. There are not only rooms dug into the rock, but also Monolithic Churches, which where cut from the massive rock and sculpted inside and outside.
India has numerous natural resources and also many mines, though, also as a result of above geology, not as much as other countries. Quite spectacular are the gem mines, which are mostly a result of the weathering of gem bearing rocks, which dissolved the rock except for some residuals, mostly clay, and the gems. As a result the mines are actually quarries where the clay is quarried and washed so the gems are separated. But there is no tradition of mining, the mines are mostly death traps and if they are closed, they are filled in as soon as possible. There is also no tradition of show mines, we have listed only two sites which are simply the surface remains, there are no underground tours at all.