1. **State the problem:** We need to find the area of a rhombus given its diagonals. 2. **Formula for the area of a rhombus:** The area $A$ is given by $$A = \frac{1}{2} \times d_1 \times d_2$$ where $d_1$ and $d_2$ are the lengths of the diagonals. 3. **Given values:** $$d_1 = 8 \text{ mm}, \quad d_2 = 6 \text{ mm}$$ 4. **Calculate the area:** $$A = \frac{1}{2} \times 8 \times 6$$ 5. **Simplify:** $$A = \frac{1}{2} \times 48$$ 6. **Final calculation:** $$A = 24$$ 7. **Answer:** The area of the rhombus is **24 square millimetres**.