FMF - Friends of Minerals Forum, discussion and message board

[GabiG]

Hello :-) I found what I think is an Agate and I would like to cut it open or slice it to see what's inside, but I don't know how to identify the direction of the banding. I found this rock on a beach on the Isle of Man (UK). There are some moss-like features on one side of the rock, and possibly some banding on another face. I marked the rock with two lines (1 and 2) showing the directions of cuts which I thought might be right, but I'm not sure which one I should use. I would really appreciate your help! :-) Many thanks.

[Bob Harman]

Uncut agates, are like unopened hollow geodes. You cannot tell the best orientation of the banding patterns or crystals on their inside . In my experience, the best way is to open your agate is to show the largest surface area on its cut side. BOB

[GabiG]

Thank you :-) I suppose that would mean cutting it along my "green line 2" . The moss-like feature has the larger surface area. The stone is an odd sort of shape and is really colorful with interesting features. But the moss feature is really pretty. It would be a shame to cut through it also.

[Daniel Bennett]

It's a good question to ask. I have ruined a few cutting them wrong. Usually if it's a whole nodule, unbroken anywhere, it can be a tough decision to make. In your case it has a few "windows" where it broke and you can see what's inside it. It doesn't seem to be a traditional style agate. Maybe it's banded chert. You can expect the inside to look about like what it looks like on its broken faces. Maybe if you cut right through the middle you may find some more banding but I wouldn't count on it. Another approach is to keep slicing/grinding it where you see banding until you get to a sweet spot and stop there and keep it as a half nodule. Hope that helps

[GabiG]

Thank You :-) Yes, I thought it might be chert as well, but I was told it was Agate. The very dark stone visible on the broken face with the moss feature reminds me of flint. Anyway, it will be interesting to have a look inside. Actually, like you suggest, it wouldn't surprise me either to find more flint inside and not much banding. But it helps to know where to cut it to begin with! :-D I think I will cut it in a way to keep the moss feature intact because I like it. I've never cut Agates before, so it's a learning experience, and hopefully if I find more like this one, I will be able to learn to better analyse features on this type of stone or banded chert to help me in the future. I've got some translucent Agates and they are much easier to inspect with a light behind them. Not possible with this one of course. Thank you again. Much appreciated.

[vic rzonca]

In a case like this, when you come to a fork in the road, take it. This may apply to your problem, GabiG.

[GabiG]

Does that mean cutting at a different angle if first cut points me to that direction? :-)

[vic rzonca]

[rweaver]

[GabiG]

Thank you again! :-)