The best thing to do is to use warm water and a really mild soap like washing up liquid, soak the earrings for a few minutes and use a soft brush like a kids toothbrush or a makeup brush to loosen the rest of the dirt. Dry them thoroughly with a soft cloth and use a silver cloth for a final polish.

Be careful if they are in a four claw or a delicate setting as sometimes dirt holds the stones in place!
References :
http://www.findjewellery.co.uk

The considerations when designing a ship are vast. a "cargo ship"can be ha huge range of ships. with are build whit Various considerations.

I shall give some things to keep in mind when designing a ship:
what kind of cargo will be carried. examples:
-container
-bulk cargo (like ore)
-heavy loads (factory parts)
-general cargo (like timber paper)
-gas
-chemicals
-refrigerated cargo (often fast ships)
-livestock

amount of cargo (big ship or small)

Sailing area is of huge influence
-are there restrictions in the ships dimensions (draft, air draft, length Breadth) when passing channels bridges and locks.
-what should be the range of the ship and at what speed
-the port facility’s does the ship need its own cargo handling gear and is it hard to manoeuvre (extra thrusters)
-does the ship need an ice classification

all in all depending on the specific use of the cargo ship its design has specific requirements.
References :
Own knowledge (Officer on Cargo ships)