Dear Dr. Nasseri,

even if your mineralogical description is very poor I dare to give a comment based on the outward expression. It looks like "cat-eye" which is a common mineral aggregate encountered in basic and ultrabasic rocks undergoing autohydrothermal alteration. I know it from picrite and diabase. It is a fine-grained aggregate of quartz and hornblende asbestos (amiant) (silica+blue asbestos), rarely chrysotile (silica+white asbestos). Even if it shows a massive habit, the needle-shaped and fibrous silicates may show a more or less strong alignment along fissures. The green mineral aggregate can, if present in well-textured aggregates used for jewelries and faceted to cabochons.

H.G.Dill

Dear Harald G. Dill ,

I do not think this mineral is "cat's eye".

It seems that this mineral is part of tectosilicates because after breaking, the pieces are still in the form of sheets. In addition, light does not pass through this mineral.

Even amphibole occurs in sheet-like fragments. The other alternative is a Cr-bearing sheetsilicate such as volchonskoite or an abnormal tint of chrysocolla. But I must admit this is nothing but poking around in the fog and I would like to abstain from further speculations like those

Dear Nasser

Your sample is very impressive!! I'm a bit prudent to call it native copper. I encountered the same occurrence in the Neyriz ophiolite. Anyway, could you please send me a photo from the polished surface?

Regards

The most widespread example of tectosilicates is the feldspar group. The brief description of chromite and serpentinized dunite leaves little room for the assumption of feldspar in this mineral aggregate which is almost absent in this basic to ultrabasic environment of deposition

Dear Nasser,

I think the rock is serpentinite and sheets of native copper. The Cu is formed likely along network of cracks. We see the one wall of several cracks. Just scratch the metal with a steel needle. If metal is scrached then it is likely metalic copper.

Regards

it is very difficult to give an expertice from this picture. But it looks like an alteration product a zeolith, especially Heulandite.

It is very difficult to give an expertice from this picture. But it looks like an alteration product a foliated zeolite, Heulandite or Stilbite.

Perhaps Cr-mineralizeation hosted dunite

Dear Colleagues,

that Cu is involved in the mineralization seems to be evident based upon the bronze luster, but as far as the green silicate intergrowth is concerned the field of speculation can only be narrowed down by a widening of the database which is very poor. We do not know the geological setting, known mineral assemblages associated with it etc.

H.G.Dill

Dear Nasser Nasseri: even if it occurs in serpentinite it certainly looks like a copper-iron sulfide, like chalcopyrite, cubanite, luzonite, and the like. Strange things may occur during serpentinisation of peridotites and dunites, I have a sample from Cuba of gold veins in serpentinite, and it is common also to find cinnabar veins in this type of altered rock. Regards, Sebastián.

A picture is by no means diagnostic, but what about a hydroxyl carbonate of the hydrotalcite supergroup (pyroaurite, coalingite, aso.)?

Dear Colleagues,

it will be an endless saga without scientifically based new data. If we do not receive new data we are at the brink of another "1000+x thread"

H.G.Dill

Dear Nasser,

Mineralogical and chemical analyses will give you the answer. Anything else will be assumptions.

regards

Walid

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Dear Nasser: you should submit these alteration minerals to al least XRD or XRF, simple hardness and strike tests can be somewhat indicative, but not precise, as there are many copper, nickel and other metal sulfides with bronze color. Definetely it is chromite, though! Regards, Sebastian.

I wonder if there exists a listwanite zone near the location on which this particular rock is taken. If so, we can easily think of a possible hydrothermal alteration of this peridotite, leading to such strange mineralizations in ophiolitic suites.

Can anybody tell me which kind of reaction might have caused this "chromite" to take on a bronce luster ? If we deal with Cu mineralization in ophiolites we have to speak of the volcanic level of the ophiolite sequence that is "minerostratigraphically" higher up in the suite, whereas chromite is found further down in the plutonic part where dunites prevail. There is a couple of mis-match in the story.

Dear Dr. Harald G. Dill;

You are right about sequential part. Although, the area might have been eroded to such lower levels and then experienced hydrothermal alteration. I have been working in various ophiolitic areas and never seen such a chromite mineralization. No chromite can provide such a metallic brown luster.. I have seen 'dull' brown with lower grades of chromite, but definitely not like this one. I am almost positive that this is a Cu mineralization.

Dear Nasseri

Please contact me for furthur discusion and guidence.

My phone number is 09143005391

Dr. Faridazad

Erratum: I wanted to say "Definitely it is NOT chromite! I forgot the NOT! Regards, Sebastian.

Agree with the view that it is likely alteration products of mafic-ultramafic rocks. It is not a mineral but consists of various mineral aggregates.

Dear Nasser: the bronze-yellow mineral with strong metallic luster is probably chalcopyrite or something similar (cubanite, luzonite...), surely other species exist in this altered rock, but nothing which cannot be identified by a XRD powder analysis. Regards, Sebastián.

I have been working in ophiolite terrain but I have not come across chromite of this sort. I believe it to be a rodingite???

A thin section of the sample will be able to clear our doubts.

It is an interesting alteration mineral of whatever was in the fresh ophiolite (which means a "snake rock").

Nasser Nasseri I agree with Harald G. Dill