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Dwarves' Earth Treasures Museum:
Bear Mountain Thundereggs
Bear Mountain, Silver City, Grant Co., New Mexico
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     The thundereggs of the Bear Mountain are well known for many decades and widely visited by local rock clubs, but they still can be found even today despite the complains by local rockhounds about not finding anything except small ones. The Bear Mountains along edge of Gila National Forest, are mainly limestone with a very hard limestone sticking out like a sore thumb on one side and there are isolated pockets of rhyolitic lava flows, the source of thundereggs. I hit on a strata enriched in the thundereggs on March 2004 and found many thundereggs containing rare sagenite needles (after zeolites), aragonite fans, black calcite crystals, waterline agates, and some with shadowing effect. The colors of the agates are typically colorless to bluish gray, and some white and rarely brownish agates have been found. I did get a couple of "freak" thundereggs with colored agates.
    I came back to it two years later, but did not had any luck with digging, and that was when I realized that I passed the narrow strata. That strata was buried under so much tailings left by diggers, and it's going to take a lot of work to uncover that strata. The agate in the thundereggs are typically colorless to blue with some white colors. It's rare to find those with brown colors and those with shadowing effects are even rarer.  I have seen excellent amethyst geodes and agates with shadowing effects from that area. From time to time, I still find some thundereggs there and there.
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Rough Appearance: Brown thundereggs with bubbly surfaces, ridges rarely showing
Agates are mostly clear with some faint banding, come in white to gray colors sometimes with blue to purple tints.
A percentage of thundereggs will have sagenite inclusions
Typical white agate March 2004 Typical Sagenite Agate, March 2007 White with some shadowing effect, March 2004
With rare aragonite "fans"
"Cave View of the Ocean", March 2004
Typical example of "Waterline" agate
Rare combo of colored agate
and waterline agate. March 2007
 Freak colored agate with sagenite
 Freak colored agate with sagenite
With strong shadowing effect, March 2008
Rare colored sagenite type
March 2008
Busy Sagenite-type
Outstanding needle-like sagenite agate
March 2008
Brownish color with shadowing effect
March 2004
Rare brownish color. March 2004 Dentritic (or Plume "balls") March 2004