Purchasing silver for silver or silver for gold
Q: I would like to know about zakat.
1. My wife has gold and silver ornaments and she is liable for zakat every year as they are above nisab. She wants to sell some of her silver ornaments and with that amount which she gets, she will purchase gold ornaments and this gold ornament she will give it to some poor and needy Muslim for the marriage purpose etc.
My question is, can she do this kind of transaction, i.e. by selling silver and with that amount she can buy gold or she can only buy silver with that money in lieu of silver. Will it fall under riba, interest etc?
2. Secondly, if we are not given cash by selling silver but the shopkeeper says that in lieu of silver sold you can purchase silver ornaments. Can we do that. But when cash is given by selling silver it is less and when the silver is purchased in lieu of silver we are getting more.
For example if we are selling a silver ornament we are getting cash of Rs.16,000 (indian rupees) and when we are not taking cash but we are purchasing silver ornament in lieu of silver we are getting equivalent of Rs.26,000/- Is it ok to purchase silver like this?
3.Can we purchase gold ornament equivalent of Rs 26,000/- or not. Do we have to purchase only silver in lieu of silver. What is the correct method to do it?
Note: The weight may vary of gold and silver. The silver weight is more and the gold we will purchase will be less in weight but the amount will be of Rs. 26,000/- or more if the gold we purchase is of more value than rs 26,000/- so the extra we will pay to the shopkeeper cash from our side. If we cannot do all the above what is the shariah method to do it, please tell me.