Explanation:

Gross raw materials are those raw materials that lose weight with time (time spent during transportation and initial processing). As a result, manufacturing units using these raw materials are located near the source of raw material itself. For example – most of the Iron and steel plants are located in the Chhotanagpur  region as all the inputs of this industry like Iron ore, Limestone, coal etc. are gross materials.
Non weight losing raw materials are known as ‘pure’ raw materials.