Rocks in Land

Hi Seniors, Experts and consultants,

I am planning to buy 12 acres of land 20 KMs away from Tiruvannamalai. This piece of land has got rocks in at least some 4 acres approximately. But this land is also attached to poromboke land of 6 acres up to the hillock, which could be used only by this land owner. A canal is running which was  developed by PWD adjacent to this land without water in it. They say, in future water may come from Sathanur dam. A road is there adjacent to this canal, which is the access for this land by trucks. This area is not being farmed for many years I think. There is no well. But nearby a farmer has dug a bore well recently, which gives a good yield of water at nearly 400 feet.  Now, my query is whether can I buy this land with rocks? My worry is, we are able to see rocks on the surface on nearby 4 acres. What if rocks are found below ground in other locations also? Near by a small hillock is also there with huge rocks. But apart from this parcel of land, in the other lands nearby there are no rocks found. Few people are having sugarcane, ground nut, paddy and plants for goat etc in their lands where they have got water. The soil is red in colour, (I thing , it is good for agriculture). As of now this land is having many bushes, trees etc, which needs to be cleaned with dozer. The land costs around 2 Lakhs/ acre for the land with patta.  My another query is, as there are many rocks found, can the rock be used for any other business related to agriculture? How can we found whether the rock is granite? Are there any methods to find out granite by laymen like me?  Can we use these rocks for making blue metal or stone dust and sell it? What kind of permission I require for doing this? Actually I am planning to plant trees (Teak, Vengai, Nelli(gooseberry), sugarcane, Goat farming and poultry. Please ignore part of this query which is not relevant for our consultants/ experts to reply. In summary, my queries are: 1. Can I buy this land with rocks? If there are rocks below the land which is visisble now what would happen?
2. Is there any way to find out whether the rocks are of Granite by a laymaen like me?
3. Are there any other business related to agri in using these rocks?
4. For using this rocks and produce blue metal (stone chips for concrete), or stone dust to use as sand, any approval is required?
5. Whether this land will suit my interest of tree farming, sugarcane and goat farming and pultry? Or do you have any other suggestion for this land?

Thank you in advance.