Ocos Geodes
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Many names have been given to geodes throughout the
world, but none so fitting as the Ocos Geode (some say
these are named for their source, the Orinoco River in Brazil,
others believe it came from the Portuguese word for
"hollow," you decide...)
Ocos formed some 130 million years ago in
basalt amygdules (a formerly open vesicle which has been
filled with a secondary mineral(s) precipitated from low temp
ground waters which penetrated into the rock). Over the
years the basalts have been weathered away and left behind
small geodes in what is now called cascalho, a dark reddish
brown soil in the Serra Geral Formation.
Ocos are mainly found in the 3000 ft elevations of the Tres
Pinheiros (Three Pines) region.  The geodes are normally
removed from the basalt by hand (which can be difficult
because their skin or outer shell of chalcedony is relatively
thin and often rope-like in formation). The Ocos are then
taken back down the steep mountains in burlap sacks or
buckets on horseback or by pack mules to the town of
Soledade to be cut and polished.
Thin shell Ocos called "casa fina" command a higher price,
but display less of the famous wavy or flame like patterns on
the rim. Ocos size is usually small (1-3 inches)
When cut, Ocos display brilliant drusy quartz linings on tan,
grey, brown or black shells with white waves or flames. Many
Ocos have inclusions in the quartz, rarely amethyst.

Ocos
Geodes

aka

Ochos
Occos
Item #OG09104460
Large Polished Ocos Geode
(Half)  

$20.00
Deep opening lined with well formed clear
quartz dotted with black goethite with small
white calcite formation.
.
This specimen weighs 5.5 oz (156g)
and measures 3.1 x 2.1 x 1.6 inches
(7.9 x 5.3 x 4cm)
Item # OG09106690
Large
Polished Ocos Geode
(Half) with pewter
prospector
$32.00
Roped exterior with drusy smoky quartz crystals with black and white wisp swirls are the backdrop setting for this
lucky prospector with his pan. Beveled edge glass stand glued to bottom of geode.
.
This specimen weighs 4.8 oz (136g) and measures 3.1 x 1.9 x 2 inches (7.8 x 4.7 x 5.6cm)
Item # OG1014A001
Polished Ocos Geode Pair
$8.00
Beautiful exterior shell with tan, white and clear wisps
on the polished edge with well formed quartz crystals
with black inclusions.
This pair weighs 20.5g and each half
measures 1 x 0.8 x 0.63 to 0.75 " (27 x 21 x 16 to 19mm)
Item # OG1014B001
Polished Ocos Geode Pair  
$8.00
Black & white shell with black, white and mahogany
wisps on the polished edge with well formed quartz
crystals in the vugs.
This pair weighs 25g and each half
measures 1.2 x 0.8 x 0.67 to 0.7 " (30 x 20 x 17 to 18mm)
Item # OG1014C001
Polished Ocos Geode Pair
$8.00
Black & white shell with black, white and clear wisps on
the polished edge with well formed quartz crystals in
the vugs.
This pair weighs 35g and each half measures 1 x
0.8 x 0.8 to 0.9 " (26 x 21 x 20 to 23mm)
Item # OG1014D001
Polished Ocos Geode Pair
$8.00
Clear and tan shell with tan, white and clear wisps on
the polished edge with well formed drusy quartz
crystals with brown inclusions.
This pair weighs 39g and
each half measures 1.5 x 1 x 0.67" (38 x 26 x 17mm)
Item # OG1014E001
Polished Ocos Geode Pair
$8.00
Black and white roped shell with black, white and clear
wisps on the polished edge with well formed quartz
crystals in the vugs.
This pair weighs 32g and each half
measures 1.6 x 0.6 x 0.86 to 0.9" (41 x 15 x 22 to 23mm)
Item # OG1014F001
Polished Ocos Geode Pair
$8.00
Black shell with grey, white and clear wisps on the
polished edge with well formed quartz crystals with
goethite inclusions.
This pair weighs 25g and each half
measures 1.1 x 0.75 x 0.75 to 0.89 " (28 x 19 x 19 to 22mm)
Item # OG1014G001
Polished Ocos Geode Pair
$8.00
Grey shell with clear band around white fortification
lines on the polished edge. Vugs have druzy quartz
crystals with goethite inclusions.
This pair weighs 23g and each half measures
1 x 0.8 x 0.67 to 0.8" (27 x 22 x 17 to 21mm)
Item # OG1014H001
Polished Ocos Geode Pair
$8.00
Beautiful exterior shell with tan, white and clear wisps
on the polished edge with well formed quartz crystals
with goethite inclusions.
This pair weighs 28g and each half
measures 1 x 0.95 x 0.6" (27 x 24 x 16mm)
Item # OG1014I001
Polished Ocos Geode Pair
$8.00
Tan shell with tan, white and clear wisps on the
polished edge with druzy quartz crystals with goethite
inclusions.
This pair weighs 25g and each half measures
1.3 x 0.5 x 0.86 to 0.9 " (35 x 14 x 22 to 24mm)
Item # OG1014J001
Polished Ocos Geode Pair
$8.00
Mottled exterior shell with unique tan, white and grey
swirls on the polished edge with well formed quartz
crystal vugs.
This pair weighs 26g and each half measures
1.2 x 0.8 x 0.68 to 0.7" (31 x 21 x 17 to 18mm)
Item # OG1014K001
Polished Ocos Geode Pair
$8.00
Black, white and mahogany are in the shell with
matching black and white wisps, with a mahogany end
accent on the polished edge with well formed quartz
crystals in the vugs.
This pair weighs 19g and each half
measures 1.5 x 0.6 x 0.6 " (40 x 15 x 15mm)