Answer:
D
Explanation:
Emerald is not a variety of corundum rather its a variety of beryl.
A precious or semiprecious stone may or may not be transparent.
The value of gemstone is derived mostly by its rarity.
Pegmatite are igneous rocks found underground near sheets of igneous rocks called batholiths. They are a source of gemstones made of topaz, tourmaline, beryl spodumene and spessartine.