Amethyst eruption

A 30 ft long 5 ft wide line of 18 inch amethysts erupt from the ground.  Each creature in the line makes a Dex saving throw on a fail they take 1d12 piercing damage and 1d12 force damage as the gemstones explode.

Using Higher Level spell slots:  The amethysts gain 6 inches in height and do an extra d12 force damage