Amethyst (likely)

Pale violet, translucent, vitreous luster, and apparent hexagonal quartz crystal faces; hardness 7 Mohs, no cleavage, conchoidal fracture, specific gravity about 2.65. The whitish lower portion may be milky quartz or an uncolored growth zone.

Forms mainly in gas cavities and fractures of volcanic rocks as silica-rich fluids crystallize. Amethyst in southern Brazil commonly formed in Cretaceous basaltic lava flows, roughly 130–100 million years ago.

Used for jewelry, carvings, ornaments, and mineral collecting. Small rough crystals commonly sell for about $2–$20; attractive larger specimens can be worth $20–$100+, while this small irregular piece is likely near the lower range.

The purple color generally comes from iron impurities and natural irradiation. Heating can turn amethyst yellow or orange, producing citrine-like material.

The image strongly suggests rough amethyst, though color may be intensified by lighting. Confirm with a white streak (should be white), glass-scratching hardness, and crystal geometry; avoid destructive tests. The reported location in Santa Catarina/Rio Grande do Sul region is highly plausible for Brazilian basalt-hosted amethyst.