Dear Sir,
The jewelry of your mother is mentioned in your querry are called "streedhan" and these are the properties of the women and she is entitled to have custody of them at any point of time during her matrimonial life and she is at liberty to dispose them off or enjoy them as she likes as she is the absolute owner of such property. Some times streedhan includes immovable property also as the relatives from natal home give the girl a landed property, residential houses or agriculture fileds etc.
There are three methods to recover streedhan from the illegal custody of the members. First I describe the cheapest and expeditious method. That is, to file a domestic violence case against her daughter in law before the metropolitan magistrate. In this application, you can file an application for interim relief also.
The other method is to file Section 406 IPC case as a private complaint before the magistrate. Here, there is a heavy burden lies upon you to prove that actually streedhan was given to you and it is lying with your husband/in-laws etc. This proof also must be "beyond reasonable doubt". Here, in this private complaint, you have to lead evidence twice and is a cumbersome process.
The alternative method is to file a complaint under Section 406 IPC listing the stridhan articles and lodge the complaint before the concerned police station. The police will register FIR ( different to earlier FIR u/s 498-A and Section 323 IPC).
There is one more method to recover stri-dhan, i.e., by filing a civil suit. It is very costly affair. So, I will not go into the details of this particular method.
Finally, I suggest you to go for Domestic Violence application for recovery of streedhan and a woman with your financial status can afford to fight this case.