Pará is a state in northern Brazil that drains the lower Amazon basin to the Atlantic coast and that supplies the gem trade principally with andalusite from deposits near the city of Marabá. The state is geologically distinct from the gem-rich pegmatite belts of Minas Gerais and Bahia further south, and its gem output is more modest in both quantity and variety. Marabá andalusite, however, is recognised in the trade for clean transparency and saturated pleochroism, and faceted stones occasionally exceeding five carats represent a meaningful niche product.

Marabá andalusite

The Marabá deposits in southern Pará produce gem-quality andalusite, the orthorhombic aluminium silicate Al₂SiO₅, in colours ranging from olive-green to reddish-brown. Andalusite's distinctive feature is its strong pleochroism: the same stone shows different colours along its three optical directions, and a faceted andalusite typically displays a play between green, yellow, and red-brown depending on the angle of view. Marabá material is well known among coloured-stone cutters for showing the pleochroism cleanly without excessive masking by body colour.

The deposits are weathered alluvial concentrations derived from regional metamorphic source rocks. Mining is small-scale and artisanal. Faceted Marabá andalusite ranges from small calibrated stones up to occasional examples above five carats, with three-to-four-carat material the most commercially typical.

Other Pará materials

Pará produces small quantities of quartz (smoky, citrine, amethyst), topaz, and garnet from various locations, alongside diamond from artisanal alluvial workings in the western part of the state. Gold mining, both formal and informal, is significant, with the historic Serra Pelada gold rush of the 1980s among the most famous artisanal mining episodes of the twentieth century. None of these other materials approach the trade significance of Marabá andalusite.

In the trade

For Skyjems buyers seeking andalusite, Marabá material is the leading commercial source and the standard against which other andalusite is measured. We look for clean transparent stones with strong directional pleochroism and saturation that displays the green-and-red play characteristic of the species. Cutting orientation matters: the lapidary chooses the orientation to maximise the display of pleochroism while preserving body colour, and well-cut stones are the difference between an uninspiring brown gem and a genuinely interesting collector piece.

Further reading

• GIA Gems & Gemology — andalusite and Brazilian deposits
• ICA — andalusite
• International Gem Society — andalusite reference