Dwarves' Earth Treasures:
Formation of Agates and Thundereggs
The solutions would pass thru the fractures within the
basalt to reach and fill the cavities while forcing the gases to escape
through any microfractures within the rock hosts. Sometimes, there
would be some minerals such as calcite and zeolites (natrolite) that already
have grown within the cavities before agate-forming solutions enter the
cavities. The agate would form from the solutions a layer by layer and
the agate layers consist of radiating fiberlike microcrystals. The agate
grows in a manner that there would be conducts(gaps) between the crystal
fibers of agate, making them somewhat porous and that's how the agates
can be dyed. The gases (or solutions) may have escaped thru the conducts
in a way the pressure cannot be built up within the cavities.
There is some dispute about whether the agates are
formed from "closed system" or "open system". The closed system refer to
a solution already filled in a cavity and becoming isolated (no additions
or subtracting) while the "open system" refer to the cavity being filled
and emptied periodically, bringing in new minerals and excluding out other
minerals such as water or gases. I will go with an idea of "open system"
since it seem to do a better job at explaining how the agates may have
formed.
1. Picture of a crack
in hollow Coyomito Agate nodule where solutions may have entered to deposit
agate.
2. Radiating structure
of the agate layers.
3. The layers of some
agates can be peeled off!
4. Examples of "Sagenite"
and Mesolite, a zeolite mineral.
5. What happens if the process
gets halted during this stage?
