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  Author   Comment  
Kelly L
 #1 
My boyfriend has had a very large uncut geode for years now (almost 35lbs) and we have discussed getting it cut but we are unsure about how to got about this. There is a rock/marble cutter nearby that has the proper equipment I am sure, but I am worried that we may do something to decrease the value. Would that be am appropriate place to have it cut open, and do we just have it cut down the middle and polished? We are in Lexington Ky and I have been googling all day and can't fine anywhere that advertises cutting anything but marble or granite as their specialty. The only other thing that I can think of is to contact the university of kentucky's geology department perhaps. I am totally out of my league there, but I'm dying to see what's inside!

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george w
 #2 
if you want it cut and polished you will have to find someone with lapidary equipment. my advice is to contact your local rockhound club. they usually have that equipment and can point you to someone who can do it for you.
Harry Polly
 #3 
Kelly,

I am assuming this is one of the local KY geodes.  If it is, I would suggest a hammer and chisel approach versus the sawing.  A lot of the KY geodes have cavities that are not in the center.  Sawing may or may not hit the cavity.  Hitting the geode with a hammer will produce a crack that you can then finish with a chisel.  I cannot tell by the pictures the diameter of the geode, but it appears to be quite large.  Cutting those large geodes require a large saw, possibily a 24 inch.  These blades get VERY expensive and anyone cutting the geode may require you to purchase a new blade if the geodes ruins theirs.  I have tried cutting several of these geodes in the past.  The end result was three blades ruined and the center hit in only aboout 5-10%.  I learned my lesson early on.  I would suggest trying a cast iron pipe cutter, but the geode appears to large for one of those. They will only take about an 8" geode.
Bob Harman
 #4 
A number of posters have asked "how to best open geodes and other nodules".

Over the past thirty years or so I have literally opened thousands of Indiana geodes so I will give my thoughts. Firstly let me say that there is no "perfect" or "best" way to open them; each geode should be evaluated as an individual specimen, differing from all others.
The size related to the estimated weight of each example should first be considered. If the example feels light for its size, this suggests an ample central cavity, or if the example seems heavy, this suggests a small cavity or a solid example. Some fresh examples directly removed from the surrounding matrix might be handled differently than those found in stream beds.   Use more care with light examples as those are the ones with the most potential.

After some initial evaluation it is time to first clean the outside thoroughly.   Recognize that when opening each example we might guess on the cavity size or a solid example, but it is unknowable as to the orientation of any secondary mineral crystals within the cavity. We might open the geode just right, or right thru the crystals in the cavity, damaging or destroying any that might be present. This simply cannot be evaluated prior to opening.

The easiest way to do the actual opening is to use a hammer and sharp object like a knife or flat head screw driver or putty knife.   For small geodes, especially those light in weight (hollow?), I prefer a small hammer. For those larger and heavier examples with thick rinds or small central cavities, I use a larger crack-hammer.  Determine where you want the example to ideally be opened and then gently whack the example. If several whacks do nothing, try a little harder in another area, but these geodes often are solid or have a small cavity. Not good, so I often give up and go on to the next example. If you have one where a crack develops on the outer surface, I then insert the knife or other flat object to widen the crack and split open the example.

Many folks who collect regularly and often buy a chain type pipe cutter. These work well for many examples, but very irregular or very large heavy examples will not be opened by this method. The pipe cutter, even used ones, can be expensive and are not cheap. Consider buying one if you collect often or regularly.  Wrap the chain teeth tightly around the geode where you want it opened and squeeze down on the long handled grips until the geode cracks and is opened.
Remember that in all cases, however you open each example, you cannot tell the orientation of the crystals in the cavity so it becomes the "luck of the draw" to open each example well or unfortunately break right thru the crystals in the cavity.      Hope this helps, BOB
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