It will be taxed as capital gain tax i.e. long term capital gain and for calculating long term capital gain you need to get it's fair market value as on 01.04.2001 and then indexed it and reduce it from the sale price and you will get the long term capital gain amount and you have to pay tax @20% on such gain.
Just get the valuation of such jewellery from a jeweller as on 01.04.2001.
And you won't have to pay any tax if you invest such amount in a residential house. If you gift that amount to your son and he invest that amount in house then you will have to pay tax on such capital gain however if you invest the entire sale consideration of that jewellery in your son's house and then gift him the house then you won't have any capital gain tax.
You can have a consultancy session if you have any query or want any further information.
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