Thought the following information will help analyzing Pokarna (w.r.t availability of Quartz mines)
Googled and found the below PDF (available from Indian Bureau of Mines - IBM)
http://ibm.gov.in/writereaddata/files/05082015162012EXPIRY%20AFTER%202014.pdf
This PDF has information on the lease expiration for various mineral types (for companies/lessee). Couldn't find an easy way to export this info to XL for better processing. On manual search I found one entry under "Quartz" for Pokarna
Company (Lessee) Area (in Hectares) Lease Expiry date
POKARNA LIMITED 21.86 05-MAR-18
and multiple entries for Chettinad (or entries with keyword Chettinad) with a total area of ~20 hectares or so. But I did notice few other companies/individuals having leased out in 50s/100s of hectares of Quartz quarries.
Used the following link to query on any pending applications with IBM and couldn't find any hits for Pokarna
http://mcas.nic.in/Mining_plan_web_Query.asp
Based on the above info, Pokarna + Chettinad (related groups) seem to have around 40+ hectares of Quatz quarry leases and from one of the above posts I did read that Pokarna's Quartz quarry is not active, which leaves them with around 20 hectares of quarry from Chettinad group (out of which Pokarna might be using few of them). It does look like that Pokarna should look for other sources for raw material (Quartz) sooner/later...how soon is a question to be answered.