Question

how do minerals form from magma? by rapidly melting in earths core by crystallizing as magma or lava cools by dissolving in ocean water by breaking down into smaller particles

Explanation:

Magma is molten rock beneath the Earth's surface. As magma or lava (magma that reaches the Earth's surface) cools, the atoms within it slow down and arrange themselves into orderly patterns, forming crystals. This process is called crystallization.
Melting in the Earth's core would not form minerals (it would keep them in a molten state). Dissolving in ocean water is not related to mineral formation from magma. Breaking down into smaller particles is weathering, which is a different geological process.

Answer:

By crystallizing as magma or lava cools