01

What to look for

Under 10x loupe: an empty cavity that has the geometric shape of the host mineral. In quartz it may appear as hexagonal forms; in corundum, rhombohedral forms.

02

What it means

The crystallographic form of the cavity can support host species identification. Combined with fluid, it becomes a fluid inclusion.

03

Expert move

Distinguish from an actual crystal inclusion by checking whether the inside is empty or fluid-filled. The walls are smooth and follow crystal faces.