6. The three views of a geometric body are shown in Figure 1. Its side view is an equilateral triangle with a side length of 1, and its top view is a rhombus formed by two equilateral triangles. Then the volume of this geometric body is $($.
(A) 1
(B) $\frac{1}{2}$
(C) $\frac{1}{4}$
(D) $\frac{1}{8}$
6. C.

The geometric body can be regarded as consisting of two triangular pyramids with a base that is an equilateral triangle of side length 1 and a height of $\frac{\sqrt{3}}{2}$. Therefore, $V=2 \times \frac{1}{3} \times \frac{\sqrt{3}}{4} \times 1^{2} \times \frac{\sqrt{3}}{2}=\frac{1}{4}$.