Step 1: Understanding Ball Clay.
Ball clay is a fine-grained, highly plastic, sedimentary clay. It is known for its high plasticity and is often used in ceramic pottery.
Step 2: Analysis of options.
- (1) Sedimentary Clay: Incorrect, ball clay is sedimentary, but it is specifically known for being highly plastic.
- (2) Plastic Clay: Correct, ball clay is classified as plastic due to its high plasticity, which makes it ideal for shaping and molding.
- (3) Coloured Clay: Incorrect, ball clay is not typically associated with color.
- (4) Residual Clay: Incorrect, residual clay is formed from weathering and is not typically classified as ball clay.
Step 3: Conclusion.
Thus, the correct answer is (2) Plastic Clay.