Dwarves Earth Treasures: Mexican Coconuts from Mestano Ranch and Las Choyas Mine, Mexico

"Mexican Coconuts"
Mestano Ranch and Las Choyas Mine,
Chihuahua State, Mexico

They were called "Mexican Coconuts" because of their nearly perfect spherical shapes, and they tend to be either filled with agate, lined with quartz crystals (geode) or both. It should be noted that "geodes" are always hollow as according to official dictionaries. The colors of agate are typically white to gray, sometimes with light bluish hue and some with very strong shadowing effects. Since the water content is high in the "coconuts", the details and colors will appear sharp or stronger when freshly cut, but will become dull over time as water evaporates from the agates. Some mineral inclusions turn yellow when exposed to sunlight and air, giving some agates yellowish to brownish look. The most prized of any Mexican Coconuts would be those with deep purple amethyst geode center with clear calcite crystals.
They have been produced in abundance but a small percentage of them actually would produce any solid quality agate and amethyst geodes. I cut a crater full of "Mine run" Mexican Coconuts(55) and got only four "Coconuts" containing solid agates. Rest are just low quality geodes, solid quartz cores, and solid geothite & calcite cores. Some "Coconuts" contained weird sagenite-like structures.
There are several underground mines such as Mestano Ranch and Las Choyas that bring out the "Coconuts" from the clay bed under the rhyolite bed. There are some evidences that the "Mexican Coconuts" as a form of fully expanded thundereggs resulting from the rhyolitic lava flowing over something very wet such as an aquifer. Something wet (aquifer?) under the rhyolitic lava flow provided an abundant source of water vapor that fully expanded the cavities within the nodules just like the thundereggs in balloon-like manner.

I also found another Mexican Coconut with thin but intact rhyolite shells that support the idea that they are the thundereggs.


Cut specimens, (thin thunderegg shell around it)	Rough look, stretched look with some "rock bubbles"

This pair is the reason why I placed "Mexican Coconuts" in thunderegg category.

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Rough Appearance: "Coconuts" with shallow ridges and "craters" all over, comes with dark, greenish or white skins
Some are geodes, others are solid agates in white to gray with bluish tint, few come with yellow rims.
The colors and details will become dull over time.

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Classic Agate-Rimed Amethyst Geode	Dark Amethyst Geode with icy calcite crystals I cracked this one open. O_O

Typical gray to white colors	Shadowing effect in agate rims

Yellow to red agate rims

Apparently, there's a mineral inside this agate that become yellow when exposed to sunlight and air. Strongly fluorescent under long-wave ultraviolet light	Apparently, there's a mineral inside this agate that become yellow when exposed to sunlight and air. Strongly fluorescent under long-wave ultraviolet light

Unusual red color.