Axiom Mining, page-133

Bulk Carriers:
For dry cargoes with a high weight to cost ratio such as coal, grain and ore, economies of scale have produced the modern bulk carrier. These usually large vessels are divided up into several separate holds covered by hatches. In port, cargo is loaded by conveyor and spouts or by crane and grab. Some bulk carriers are geared (usually a crane is located between each hatch) to allow the loading and unloading of cargo at berths without the need for shore equipment.

For unloading, cranes with grabs are the norm although specialised equipment may be used for certain cargoes. When vessels unload using cranes and grabs, personnel and vehicles will often be placed inside the holds to assist the process. Cargo will usually be unloaded into hoppers and will then be transferred by conveyor to silos or open storage, smaller vessels may discharge directly into road vehicles.

The above comes under the heading of cargo ships so when you see cargo ships on the marine maps it could be any one of a number of different types of cargo ships. The only one that differs are oil tankers and that is probably due to the volatile fuel it carries.