dear expert as yo see in photo attached
in my village NW yemen, while i am checking area affecting by faults i found this viens in wadi, first of all i checked the magnatic no response, second thing if i add HCL give me some reaction in vein it self, third thing it is very hard to scratch and the color of streak is pale brown and dark grey in part, also give me some reflection colors under normal microscope.
the outcrop is sandstone, and area is wadi form by fault action, same area around 4 faults parallel.
i thought should by magnetite no magnet response and even after heating that means maybe not also hematite or geothite. and from streak color will not be pyrolusite (mno2), this is a physical properties study as difficult to perform chemeical analysis due to situation in yemen ( no opreational equipment).
please advise me from that i can conforim what is this mineral or i have to perform xrf and xrd to know , please advise
- by the way area adjacent to hot spring
Dear Mr. Alshagdari:
Even if you exclude oxide-hydroxides of Fe („limonite“) or Mn („wad“ / “manganomelane“) I assume based upon the picture what is called in German “Schwarzer Glasskopf” (black collomorphous Fe-Mn oxide-hydrates). It seems to be a subhorizontal joint and the concentration of the minerals supergene in origin by per descensum meteoric waters.
XRD and XRF (chemical analysis) would direct your thoughts in the right direction.
Kind regards H.G.Dill
Dear Mr. Alshagdari: I found a lot of these before along sear zones, they are mixtures of hydrated iron oxides (probably goethite and limonite) are present as mammillae and botryoidally forms, giving the shear zones and faulting a remarkable feature. Plz check these: A New Uranium Occurrence, Gabal El-Missikat Prospect, Central Eastern Desert, Egypt
Regards
It looks like botryoidal hematite to me. Goethite has this form as well. Botryoidal means "bunch of grapes". It is unlikely that this could have formed during active shearing along a fault. More likely, the vein filled an open fracture, which may have been associated with the regional faulting that you describe. Here is a picture of botryoidal hematite.
Opaque minerals could be identified by ore microscopy, physical properties, XRD, SEM and mineral chemistry. Due to the lack of lab. equipments you got, we just try to help based on the provided information including the pictures, mineral forms, host rocks and minerals association. Accordingly, we can confirm that you have a low temperature mineralizing fluids, open space and cavity filling process. From the provided information we can't confirm the type of opaque mineral exactly. The botryoidal form of the opaque minerals is well known for goethite, hematite and pyrolusite and may be others. You also have a carbonate mineral which could be most probably calcite or siderite, that are found frequently associated with these minerals. I advice you to do polished slab and ore microscopy study.
Best Regards
Hi Mr. Alshaghdari
I think it's iron oxyhydroxides, hematite / goethite-limonites
Best regards.
I hace the same opinión of David Malone.It Is botryodial hematites and the structural geology confirms its origins.
The pictures look like it is some kind of Mn oxyde/hydroxide vein. The botroidal form and the color of streak are in accord , and also the presence of calcite. Looks like an open filling of hydrothermal fluid. Is there any volcanic activity in the area? what age?
In my opinion they look like some iron or manganese mineralization and the Botryoidal structures may formed by volatile contents I mean the area may have formed in high temperature, we can see some gaps between the the mineralization (according to David Malone), what I look is the wall of the gaps have the minerals formed by volatile content. In contrast, they may formed by meteoric water what Harald G. Dill suggest, or I think it may be a iron concretion.
secondly, look is there any volcanic activity or hot spot near that area now or in the past?
Probably, botryoidal hematite or goethite, as already suggested by several friends.
Ramachandran Chandran
yes around there is hot spring area and still active
O also think it is aggregate of Fe-Mn oxides/hydroxides. A useful field teste with some drops of H2O2 will indicate the presence of Mn oxides by effervescence.
Regras,
Lincoln
Lincoln
what this test will guide my and what you mean by effervescence
This simple test will indicate the Mn oxides presence. Just this. The reaction will liberate O2 and small bubbles (similar to boiling).
- Badges
- Science topic
- Similar topics
- Geoscience
- Atmospheric Sciences
- Atmosphere
- Air