FMF - Friends of Minerals Forum, discussion and message board

[Ken]

I can't find anything that looks like this stone. It appears to be a piece of quartz that has undergone some sort of modification. It's the strangest looking quartz I've ever come across, anyone ever seen anything like this and is this quartz at all?

[James Catmur]

I see two different rocks.

The simple answer is 'no' - they may contain quartz but they are not quartz. Where are they from? Could you do a few tests? I expect a geologist might be able to tell you what rock they are if they know the locality.

[alfredo]

To me they all look like jasper or chert, both of which are types of micro-granular or microcrystalline quartz that are impure (due to abundant inclusions of iron oxides, chlorite, clays, etc) and consequently almost opaque.

[Amir Akhavan]

Most likely chalcedony, as Alfredo said.

The looks can be deceiving ;-)
The rock in the attached photo is > 95% quartz.

[SteveB]

The clear white veins are form(s) of quartz, some parts are tending towards agate . Chalcedony is my guess there, possibly quartzite.The brown though no idea. Its a water rounded riverstone basically. If you found it yourself and know precisely where it was, You probably should return there and search river side upstream for rough boulders that match. Ie patchy brown & black with white/clear veins. You might be able to find the host rock and be able to then take proper hardness tests of the brown portions, maybe be able to chisel off pieces that dont contain the veins of quartz for specific gravity testing and maybe xrf analyis. Have you tried to see if hydrochloric acid drops react with it? Your whole example is a rock not a mineral. A rock is made up of minerals and its pretty confident the white veins are quartz which are a common intrusion into host rocks that get cracked. I would geuss the host rock is slightly softer than the quartz accountng for the orange peal surface texture. More legwork required I suggest.

[Ken]

It's one rock with two different look. It has a hardness of 7.0 and no part reacts with acid. This rock was found in the California desert east of LA. There's mountain that has a slot cut into by rain water, I walked about 20 yard back in the slot and picked this rock out of the walls along with several other odd rocks. A lot of the rocks from there look as if they have been put thru something, they just look odd.
Here's a piece of quartz that had some sort of orange dust inside of it.

[Bob Harman]

Not at all odd, in fact very common. That is the expected look for a massive vein of quartz whose exposed surfaces and hairline cracks/crevices have been exposed to rusty iron oxides for millennia.

The exposed surfaces are dingy rusty brown while the freshly exposed quartz surfaces are fresh and clear or white. BOB

[Bob Harman]

For reference, look at this Indiana quartz geode.

The geode, long ago, weathered out of its host limestone rock. The quartz outer rind has been exposed to the elements for millennia and has become rusty brown while the recently opened quartz interior is fresh and bright.

Over the ages, if a very thin hair-line crack had ever developed allowing moisture with iron oxides into the central cavity, rusty staining would be there as well. Then the geode would most likely not be worth collecting. BOB