Marambaia is a pegmatite district in the eastern portion of Minas Gerais, Brazil, lying within the broader Eastern Brazilian Pegmatite Province that has supplied the world with aquamarine, morganite, heliodor, tourmaline and a long list of less familiar rare-element minerals. The district sits on the metamorphic terrain of the Aracuaí orogen, where late-stage granitic pegmatites intruded mica schists and gneisses during the closing stages of Brasiliano-Pan-African collision around 535–480 million years ago.

For the gem trade Marambaia is most strongly associated with aquamarine of a clean, light to medium blue tone, sometimes carrying the slightly greenish cast typical of unheated Brazilian beryl. Rough from this district has historically reached the cutting houses of Teiófilo Otoni and Governador Valadares, the two cities through which most eastern-Minas pegmatite production passes before export. Stones cut from Marambaia rough often display the long, clean prisms that allow large emerald cuts and elongated cushion shapes, a function of the habit of beryl in the host pegmatites.

The district has also yielded fine specimens of green and pink tourmaline and, less commonly, columbite-tantalite of mineralogical rather than gem interest. Production has been intermittent rather than industrial in scale, with garimpeiro workings rather than mechanised open pits dominating the recovery picture. As with most pegmatite-hosted aquamarine, the colour of Marambaia material is principally controlled by trace iron, and routine heat treatment to drive off any greenish or yellowish overtone is common practice in the trade.

From a buyer’s perspective Marambaia is best understood as one node in a broad pegmatite belt rather than a brand in the way Santa Maria de Itabira or Espirito Santo’s Marbella aquamarines have become. Origin determination at gemmological laboratories rarely distinguishes individual pegmatite localities at this level of resolution, so trade descriptions tend to default to “Brazilian aquamarine” unless an unbroken chain of custody from a known mine is available.