这个地区的岩石主要由白云石组成，质地非常坚硬。

The rocks in this area are mainly composed of ___dolomite, making them very hard.

这座山的岩层主要由白云石构成，呈现出独特的白色外观。

The mountain's rock layers are mainly composed of ___dolomite, giving it a distinctive white appearance.