Geodes and Agates

>> Sunday, March 15, 2009

Geodes are defined as “essentially rock cavities or vugs with internal crystal formations or concentric banding.  The exterior of the most common geodes is generally limestone or a related rock, while the interior contains quartz crystals and/or chalcedony deposits.  Other geodes are completely filled with crystal, being solid all the way through.  These types of geodes are called nodules.”    Another source states,  “Geodes are spherical or oblong rocks filled or partially filled with minerals.  When a geode is broken the minerals inside are revealed.  Most geodes are completely filled with minerals, most often quartz.”  We here in Kentucky are in one of the few areas of the U. S. where geodes are found in abundance.  The kids pick them up on a regular basis.  They generally look like any other rock, although they most generally are fairly round.  It is when they are broken open that the beauty is revealed.  Most that are found are hollow and thus feel quite light in weight when picked up.

geode1 The photo above was taken from an internet site.  This one was fairly large.  They have been found as large as two feet across.  In Ohio the largest in the world has been found and can be toured as one would tour a cave.

Mar            15th 011 Here is a very small geode that I found sometime ago.  In the next photo I will show you what was inside.  It didn’t feel hollow and when opened it proved not to be but was full of crystals.  Some are much prettier than others.  One geode hunter commented that out of about 100 he picked up he kept only 6 that were quite nice.

Mar            15th 012 By clicking on the photo you can see somewhat better the crystal formations.  Below is a picture of one that was partially hollow, although not especially pretty.  Again, it is quite small.  Most often geodes are found in the small streams in the area.

Mar            15th In Eastern Kentucky, in 5 or 6 counties, solid geodes are found that contain agate.  Agate is a “waxy variety of cryptocrystalline quartz (chalcedony) in which the colors are in bands, clouds or distinct groups.”  Agate is used quite often in jewelry.

Kentucky_2005_tn_190x161 To the left is a photo of an agate geode that has been cut and polished.  No two are alike and the colors vary greatly.  Although they are not considered a precious gem stone they still fetch a bit of money.  I recently found a solid geode that was broken across and I thought maybe I had found agate.  I even found a photo of a piece of agate that looked somewhat like it.

044 Here  is the photo from the internet.  Of course this geode had been cut and the face was smooth and polished.  In the picture below is my find, not so smooth but with much the same color.

Mar            15th 001 I watched a very interesting couple of videos dealing with finding agate, cutting and polishing it and making it into jewelry. The individual high-lighted in the videos gave his e-mail address so I sent him a note along with a couple of pictures.  Sadly, he informed me that I hadn’t found agate at all, but my geode is macro quartz.  Just the same, I think it would be pretty neat to get it cut (which has to be done with a diamond blade) and maybe use it as a paper weight.

Anyway, come on over and we will go hunt up some geodes.


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