Thunder eggs vs Geodes

So what's the difference between thunder eggs and geodes.  The lady at the Rock Hound state park in NM said geodes are hollow with crystals and thunder eggs are solid.  Problem was she had numerous rocks labeled as thunder eggs that had voids in them. I tried Wikipedia for help. "A thunderegg is a specific geological structure. A thunderegg may be referred to as a geode if it has a hollow in it, but not all geodes are thundereggs because there are many different ways for a hollow to form.  Okay, so not all geodes are thunder eggs, but just because a thunder egg has a hollow doesn't preclude it from still being a thunder egg.  I guess the geological structure or formation process is the key.  Okay, here are some pictures of a geode and thunder egg?  Interesting-facts-about-geodesThe thunder egg was found at NM Rockhound State Park.  Yes they let you dig in a state park for rocks.

I found this thunder egg in the park.  It has a solid quartz center (Needs some polishing)

I found these nodules near the NM AZ border.  I suspected they might be geodes.

Geode with Tabular quartz crystal

Geode with dirty center (chalcedony)

Geode? No void/vug

Geode with tinted green Chalcedony

These have a hollow inside with what appear to be chalcedony

NM Trip: Rhyolite

Fence and house made of "candy" Rhyolite

Next stop on our vacation was to a town called Truth or Consequences in search of Rhyolite.  Not sure what to expect from a town named after a TV game show. The particular rhyolite we were looking for is called "candy" rhyolite by the locals.  This rhyolite has enough quartz in it that it polishes up fairly nice.  The instructions we received to get to the site were not very helpful.  The road we were to travel on split into several other roads and then split again.  GPS coordinates would have helped.  We asked somebody at a nearby shooting range if they knew anything about it and they said they were from Albuquerque, although he did mention his interest in the diamonds found in Arkansas.  After searching for about an hour and getting eaten up by some fire ants we gave up and looked for Rhyolite in the town. We found a house made of Rhyolite (see above)!  If at first you don't succeed, just buy a chunk of Rhyolite from a nearby rockhound store (see below).

Purchased Rhyolite from Rock Store :-)

Rockhounding trip to NM: Fluroite, Barite, Galena and more at Blanchard Mine

Nice Specimen with Blue Fluorite

Usually once a year in the fall or spring my wife and I take a one week vacation doing some site-seeing and rock hounding.  Most of our rock-hounding on this trip was technically outside of the Rockies in southern New Mexico, but its still rock-hounding.  Our first stop was at a world famous mine outside of Bingham NM.  We had tried to call the caretaker of the mine several times, but our cheap cellphone kept telling us no service.  Since the site was only 30 miles east of the Interstate, we took a chance to see if they were open for business.  While it took some time to get someone to open the store, eventually the caretaker invited us in, we signed a disclaimer and followed a provided map to the mine site. This site is a fee only site, so you pay a flat rate of $10 per person to rockhound.  You may take as much as 20lbs of material per person.  This seemed like a lot of rocks at first, but when the primary minerals are Galena, Barite and Fluorite the weight adds up quickly.  The caretaker was somewhat upset by an individual who wanted to take 120lbs out the previous week even though you sign paperwork that says all you can have is 20lbs per person.  We followed the map to the mine and began exploring.  Both my wife and I looked for an hour or so til she found some bluish fluorite near a mine entrance.  It appeared that someone had done some field trimming of specimens there and there was quite a bit of debris.  We decided to go through the other person leavings and we ended up finding some nice specimens.  We guess this was from the guy who visited the previous week and tried to take out 120lbs.  This fall day the temperature was in the upper 70s and we were happy for a breeze that picked up at noon.