It is interesting that you cannot import Perishable ,precious and semi precious stones,gold and silver in any form through Courier services BUT you can import through Postal Channel.
The gold,jewellary,silver are subjected to price verification from Expert jewellary assessing officer. The preshible also subjected to test for fitness for human use from various testing and inspecting agency.
Also gold is considered as foreign exchange,therefore, it has to satisfy all regulationS issued by the RBI.