Final answer:
The four main geological settings/genetic models for gem beryl are metamorphic, pegmatitic, hydrothermal and magmatic.
Step-by-step explanation:
The four main geological settings/genetic models for gem beryl are metamorphic, pegmatitic, hydrothermal, and magmatic. Metamorphic: Beryl can form in metamorphic rocks such as gneiss and schist through intense heat and pressure. Pegmatitic: Beryl can also be found in pegmatite veins, which are coarse-grained igneous rocks formed from the cooling of magma.
Hydrothermal: Beryl can be formed in hydrothermal veins which are cracks in rocks filled with hot mineral-rich fluids. Magmatic: Beryl can be found as an accessory mineral in granitic rocks which form from the solidification of magma deep within the Earth's crust. These different settings and models can explain the variety of geological environments in which gem beryl can be formed.