• Option G: a long thin geode pair, shaped like a jalapeno. The border is a swirling white and dark brown feather agate, with the interior lined with light druzy.
  • Miscellaneous Oco geodes arranged face-up in dry black beans showing their glittery quartz interiors.
  • Miscellaneous Oco geodes arranged face-down in dry black beans showing their ropy rock exteriors
  • Option G: detail of one of the halves of the geode, the interior lined with colorless druzy with a white backdrop, highlighting small black spots under the druzy.
  • Option G: detail of the other half of the geode, with a mineral formation at one end
  • Option G: detail of the mineral formation, with a black crystal coated in druzy, a hollow point-like form, and a fuzzy-textured white mineral within it.
  • Option G: the geode with halves placed together closed, displaying the ring-like and ropy patterns of the exterior in gray and orange-brown.
  • Option G: Scale image of the geode pair face-down on a measuring mat, measuring approximately three inches long.
  • Option H: the geode partially open, one side turned to show the outside which is a ropy pattern in light tan.
  • Option H: off-round geode pair, light colored with a feather agate edge of white and light brown, and a colorless quartz interior.
  • Option H: Detail of one of the two geode halves, with excellent feathering pattern around the edges and some rough brown areas in the interior.
  • Option H: Detail of the other half of the geode, with lighter blonde brown and white feathering and glittering colorless druzy inside.
  • Option H: the geode with halves placed together closed, displaying a ropy texture with rings.
  • Option H: Scale image of the geode pair face-down on a measuring mat, measuring about an inch and a half in diameter.
  • Option I: a round geode pair, the interior filled with a thick layer of colorless quartz crystals and the edge a light feather agate swirl of white and light brown.
  • Option I: the geode pair with one side tilted to show the exterior is a pale cream ropy texture.
  • Option I: detail of one half of the geode, with a large point inside that is covered with a fine sugary druzy
  • Option I: Scale image of the geode pair face-down on a measuring mat, measuring about an inch and a half in diameter.
  • Option I: detail of the other half of the geode, lined with chunky colorless quartz crystals and a nice feather agate rim.
  • Option I: the geode with halves placed together closed, displaying the circular ropy patterns on the exterior.
  • Option J: teardrop-shaped geode pair with dark thick agate and a small hollow lined with fine druzy.
  • Option J: The geode pair on their side, emphasizing the agate pattern has flat parallel lines on one side versus the swirling pattern around the rest.
  • Option J: Detail of one of the geode halves, a dark semi-translucent chalcedony with swirls through it composed of white spots, with the spots aligned with solid straight lines on one side.
  • Option J: detail of the other half of the geode, with the spotted pattern turning into white feather-like patterns at the edge. The druzy inside is hard to see due to the depth of the small hollow.
  • Option J: Scale image of the geode pair face-down on a measuring mat, measuring approximately two inches long.
  • Option J: the geode with halves placed together closed, with the exterior a brown-yellow color with smooth and rough areas.
  • Option K: the geode pair tilted to show the swirls of the interior connect to the swirling ropy pattern on the exterior of the piece.
  • Option K: an off-round geode pair with one half larger than the other. The interiors are lined with colorless quartz which turns into white chalcedony streaked with swirls of darker brown and yellow-tan.
  • Option K: detail of one of the geode halves, with excellent feather geode patterning along edges and some rings of agate at one end.
  • Option K: detail of the other half of the geode, with a thick border of swirling agate reaching the surface.
  • Option K: the geode with halves placed together closed, showing an irregular shape and brown-yellow ropy patterns covering the exterior.
  • Option K: Scale image of the geode pair face-down on a measuring mat, measuring about an inch and a half in diameter.
  • Option L: oval geode pair with white swirling agate edges and the interior lined with colorless quartz.
  • Option L: geode pair showing the exterior of one half is a rough brown rock without much form. The other half has a larger quartz crystal inside
  • Option L: detail of one half of the geode, lined with colorless quartz and with a swirling white agate border with some feather patterning.
  • Option L: detail of the other half of the geode, with one well-formed larger quartz crystal inside
  • Option L: detail of the piece with the quartz point inside in different lighting.
  • Option L: the two halves of the geode placed together closed, with a rough exterior of white and yellow-brown ropy forms.
  • Option L: Scale image of the geode pair face-down on a measuring mat, measuring nearly two inches long.
1 39

Oco geode matched pairs

Oco geode matched pairs

$12.00 USD
$12.00 USD
Sale Sold out
Shipping calculated at checkout.
Select your own...

 ✨ More options: A-F

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.

View full details