US Dollar
Australian Dollar
Euro
CAD
Product Description
Polyhedroid Agate Rare Polished Rock Paraiba Brazil
This lovely Polka Dot Agate nodule or geode was sliced and polished on one face, left natural everywhere else and it has a small natural agate crystal pocket center.
This is a gorgeous rare Polyhedroid Agate and it is 8 inches by 2.4 inches and 1.5 inches thick.
It has 2 natural tiny vugs or pockets.
Unlike the typical smooth, concentric banding seen in most agates, Polyhedroid Agates feature bands that have sharp, angular formations that resemble polyhedrons resulting in striking, geometric patterns.
Polyhedroid Agates are very rare. They were only found in one location in the world, the Paraíba region in northeastern Brazil. There has been no mining of Polyhedroid Agates in recent years. Most were mined during the 1970s.
The agate nodules can be solid or hollow and the best grades have distinct, colorful fortification agate bands that follow the typically triangular or trapezoidal shape of the Polyhedroid Agate.
The geometric nature of polyhedroid agate is believed to result from the formation of gas bubbles in the volcanic rock, which are then transformed into polyhedral cavities through crystallization processes. As the agate forms, the silica deposits mimic the shape of the cavity, which in the case of polyhedroid agates, results in the sharp, multi-sided shapes that give the stone its name.
They are some of the highest quality agates available, and are able to be polished to the highest mirror glaze finish that quality agates can obtain. These agates rarely have fractures or other imperfections. Most nodules are quartz with black, gray, white being the predominant colors of the Polyhedroid agates. Shapes can be a variety of geometric forms with the right triangle or the equilateral triangle shape being the most desirable shapes.
