FMF - Friends of Minerals Forum, discussion and message board

[Ken]

Not sure what this stone has been through but it has cavities that are filled with tiny crystals. Most of the crystals appear to be under 1mm in size. Some are growing in clusters and branching out, others appear to be growing out of a yellow powdered substance. The entire inside of the cavities are coated with crystals from end to end.

[Bob Harman]

It would be of help to know where the stone was found. Anyway, whether your stone is of a fine grained igneous or metamorphic origin, it has veinlets of quartz with small drusy quartz crystals lining the small cavities. Some of these quartz crystals have a secondary coating which could be any of a number of things from a clay mineral to aragonite etc etc; just can't tell from the photo.
Bob

[SteveB]

I agree with Bob. The larger grey mass could be basalt but also other things, the reddish patch on the right looks like a wide crack injection of a variety of the grey material. On the cavity closeup are the drusy crytals of quartz but where that material joins the grey rock it looks like red chalcedony with possibly banding forming. So I’m wondering if agates are present in the area it was found. The non-grey materialis all quartz just varieties as Bob pointed out. A soak for a week in a bucket of water with washing up liquid and then a hosing should shift remaining surface dirt and organic matter. Wont improve colour much or at all but your macro photos should sparkle more. Interesting display piece.

[Ken]

This stone was found in the California desert. A lot of stones from that area look as if they have been altered from their original state, a lot are broken, highly fractured and some even show signs of some melting. I am not sure as to what mineral this stone is but it appears to be a combo of two or more minerals.

[Bob Carnein]

Stones like this are much easier to identify if they have been broken to expose a fresh surface. I'd suggest breaking it, posting a good photo of the broken surface, and then trying some simple tests (hardness, etc.).

[Ken]

I don't want to attempt breaking it so will a cut off piece be good enough, maybe a cross-section?