What type of structures are crystals considered in relation to their form?

Crystals are considered true geometric structures because they have a highly ordered arrangement of molecules that repeat in a specific three-dimensional pattern. This ordered arrangement results in distinct shapes that are often characteristic of the type of crystal being formed. This geometric precision is what enables crystals to exhibit unique physical properties, such as distinct facets and angles, which can be identified under polarized light.

In contrast, amorphous structures lack this ordered arrangement, resulting in a more random, disorganized form. Granular refers to materials composed of small grains or particles but does not convey the specific repeatable and defined structure of crystals. The term soluble pertains to the ability of a substance to dissolve in a solvent, which is not relevant to defining the geometric properties and structures of crystals.