• Option A: tear-drop shaped pair with white feathery pattern along the edge turning into swirling red hues at the base. There is a large quartz crystal inside the geode.
  • Miscellaneous Oco geodes arranged face-up in dry black beans showing their glittery quartz interiors.
  • Miscellaneous Oco geodes place face-down showing the ropy textures of their exteriors.
  • Option A: Detail of one half of the geode, with red coloration showing through the interior druzy and a large quartz crystal hanging from the top.
  • Option A: Detail of the other half of the geode, with a cluster of larger quartz crystals in the center and partially covered with a sugary white overgrowth layer.
  • Option A: Detail of the quartz cluster in the center of the geode, well-formed quartz points with a small rainbow inside one, and partially coated in sugary white overgrowth.
  • Option A: Detail of the larger quartz crystal among the druzy in the first half, coated with a sugary layer of growth.
  • Option A: The geode pair placed together closed, showing ropy swirling patterns of brown and white.
  • Option A: Scale image of the geode pair face-down on a measuring mat, measuring approximately one and three quarter inches in diameter.
  • Option B: An oval pair of geodes, lined with chunky colorless druzy with yellow-orange iron staining through half.
  • Option B: The geode pair with the back of one showing, displaying the ropy pattern of the exterior.
  • Option B: detail of one half of the geode, the top half colorless druzy and the bottom half stained orange. The edge has swirling black and white patterns with some vivid orange mixed in.
  • Option B: the other half of the geode with the top half stained orange and the bottom half colorless, with a druzy-covered protrusion in the center. The druzy has large crystals.
  • Option B: the geode with halves placed together closed, displaying the circular ropy patterns of the exterior in gray and orange-brown.
  • Option B: the geode with halves placed together closed, showing a textured yellow-brown side without ropy pattern.
  • Option B: Scale image of the geode pair face-down on a measuring mat, measuring approximately two inches in diameter.
  • Option C: a tear-drop shaped geode lined with chunky colorless druzy, which turns to white at the edges and has swirling feathery patterns in light brown.
  • Option C: the geode pair held up to the light to illustrate it is semi-translucent
  • Option C: Detail of one half of the geode, with good large druzy crystal size and light coloration around edges
  • Option C: Detail of the other half of the geode pair, with good large quartz crystals and good feathery borders
  • Option C: the geode with halves placed together closed, with a fairly smooth yellow-brown exterior.
  • Option C: Scale image of the geode pair face-down on a measuring mat, measuring approximately two inches in diameter.
  • Option D: A teardrop-shaped geode pair, light off-white color agate borders with the interior lines with colorless quartz, and an orange ring pattern at the tip.
  • Option D: Detail of one half of the geode pair, with excellent white and colorless crackle-like pattern to the cross-section of quartz crystals. The border is a milky off-white with ringed agate patterns
  • Option D: Detail of the other half of the geode, lined with well-formed quartz crystals with some small pieces of black mineral.
  • Option D: Detail of a pocket of botryoidal agate growth inside the geode, coated with fine druzy
  • Option D: detail of half of the geode held up to light, showing its translucency and the interior glowing. There are well-formed quartz crystals lining the piece.
  • Option D: the two halves of the geode placed together closed, with the exterior a grayish stone with a grainy tan coating and pock marks.
  • Option D: Scale image of the geode pair face-down on a measuring mat, measuring a bit over two inches in diameter.
  • Option E: A round geode pair, half white and half a swirling red-brown and white agate, with the interior lined with colorless quartz.
  • Option E: the geode halves held up under light to show the white half has some translucency
  • Option E: Detail of the other half of the geode, with mirror-image of the swirling red and white agate pattern and some larger quartz crystals in the interior.
  • Option E: Detail of one half of the geode, the top half a creamy white and the bottom edge lined with rings of red-brown and white agate swirls. The darker outside can be seen through the druzy interior
  • Option E, the geode composed showing the outside, with chalcedony separated into white on top and dark red-brown and orange below
  • Option E, the geode composed showing the same coloration on the other side, with chalcedony separated into white on top and dark red-brown below
  • Option E: Scale image of the geode pair face-down on a measuring mat, measuring about an inch and a half in diameter.
  • Option F: an oval geode split in half, with the edges a swirling white agate with gray and red-brown tones, and the interior lined with colorless druzy
  • Option F: Detail of one half of the geode pair, with several black pointed crystals coated in a sugary druzy, and a hollow white hexagonal crust
  • Option F: detail of the other half of the geode pair, with chunky quartz druzy lining the interior and the border a rippled white agate
  • Option F: detail of the white crust formation inside the piece, a fine sugary white layer shaped like a partial hexagonal prism. Looking down the end, there is a smaller partial hexagonal crust inside.
  • Option F: Another angle on the crystals in the interior, a spray of black points with a colorless quartz crystal, and the white crust glittering like a sugar cube.
  • Option F: Detail of the glittery small black crystal points.
  • Option F: the two halves of the geode placed together closed, with a rough exterior of white, yellow, and brown ropy forms.
  • Option F: Scale image of the geode pair face-down on a measuring mat, measuring about one and three quarter inches in diameter.
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Oco geode matched pairs

Oco geode matched pairs

$12.00 USD
$12.00 USD
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Locale: Brazil

Approx size: length of sliced face ranges 1.5"–3.25" (1.75" avg)

Approx weight: 70–120g (100g avg)

 

Oco geodes traditionally originate from the Três Pinheiros region of Brazil. They form when gas bubbles are trapped in molten volcanic rock. In the silicate-rich environment, quartz and chalcedony (a cryptocrystalline form of quartz) grow over time to line or even fill the cavity. The geodes often have agate (color-banded chalcedony) caused by variations in the color-causing trace elements available in the environment as the crystals grew. On the outside, the geodes typically display a ropy swirled or circular pattern, though they can look like a simple rock.

Each geode is a world unto itself, a product of the unique circumstances of its formation. Ocos have a large color palette: primarily warm tones of brown, red, orange, yellow, white, black, and grays. The swirls on the outside can extend into the geode in the form of a feathery swirl pattern visible around the edge of many specimens, which people refer to as ‘feather agate.’ The geode is lined with a quartz druzy but can contain additional complex crystal formations, including different varieties of quartz. Many Ocos are translucent enough that shining a light through the back can illuminate the interior.

UV reactivity Oco geodes aren’t known for their reaction, but some may fluoresce white or a radioactive shade of green. This is visible in the chalcedony base; interior quartz crystals typically do not fluoresce.

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