Geode or Nodule or Thunderegg or ?? Options

[JJCA]

Hello. I am new to this resource but hoping you all can help. I inherited my grandfather's rock and mineral collection years ago -- he grew up in Leadville and his father ran a dry goods store-- miners would often trade some of their finds for goods. I am unpacking some of the stuff and am not sure what one of the specimens is. I believe it is likely a geode or thunderegg but am not sure. It is a little larger than a softball and feels rather heavy (not super hollow). I have a neighbor with a rock saw that has a diamond blade and he said I can use it to cut open the rock. Does anyone have advice or guidance for doing so -- specifically in terms of how to get the most ideal cut to show what's inside, or is it mostly just luck if there are no real defining exterior features that would provide a hint? Is there any reason not to open the rock (in terms of losing its "value" or causing significant damage to it)? Thanks so much for the help in advance! Two pics attached.

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[Denise]

Welcome to the CP forums! Very interesting looking. It is hard to tell exactly what it is just by a picture but it could be a Geode or Thunderegg. Cutting it in half would show the stone much better, especially if it is a Thunderegg or Geode. Just make sure you keep the stone wet when cutting it. The dust is very dangerous if inhaled. You can see some of our Thunderegg cutting videos here where Dan gave a few tips on cutting them.

"ColoradoProspector - YouTube videos"

I hope this info helps some and we would love to see pics when it is cut!