For maintaining the fibrous or flaky nature during size reduction, asbestos and mica are preferably ground in which mill?

Introduction / Context:
Some materials, such as asbestos and mica, have valuable properties due to their fibrous or flaky morphology. Size reduction must preserve these shapes to retain performance in downstream uses (e.g., reinforcement, insulation, pearlescent pigments).

Given Data / Assumptions:

• Materials: asbestos (fibrous), mica (platy).
• Objective: reduce size while preserving morphology (minimal excessive shattering).

Concept / Approach:
Rod mills provide preferential grinding that tends to break at grain boundaries and minimize overgrinding and slabbing compared to ball mills or impact devices. The linear contact of rods promotes selective grinding, which is better for fibrous/flaky materials. Hammer mills and crushers impose high impact/compression, which can pulverise and destroy morphology.

Step-by-Step Solution:
Recognise the need to avoid excessive impact.Select a gentler, preferential grinding device: rod mill.Reject high-impact crushers for this duty.

Verification / Alternative check:
Mineral processing texts recommend rod mills for mica/asbestos to maintain aspect ratio.

Why Other Options Are Wrong:
Hammer/gyratory/rolls: impact and compression cause plate fracture and fiber shortening.

Common Pitfalls:
Assuming the highest energy device produces the best product; morphology preservation requires controlled breakage.

Final Answer:
Rod mill