How to Identify Carbonates in the Field 

Agreed. And now video can share that experience far more effectively than ever before.

Thanks. Hope you find it useful in the field.

Yep. Limestone is tough on gear and feet!

Thanks Alex. More on the way.

It's a great time to be a geologist :)

There are a few secondary minerals of value with yellow ochre coulours (bismuth, antimony and molybdenum in particular), but the vast majority of mustard-brown powdery secondary minerals are goethite and jarosite after carbonate minerals.

Thanks. Glad you found it useful.

Thanks very much. Glad you found it useful.

Thanks. Glad you liked it.

Thanks again for your comments!

Thanks.

Thanks Ali.

You're welcome. I hope it helps to improve your field observations.

Hurts so good!

Thanks very much Daniel.

Thanks. The weathering surface of sandy carbonates can closely resemble scoria, particularly when the carbonate has some iron or manganese to stain everything dark brown or black. The sudden transition to a grey core is a giveaway for carbonate.

I only carry 10% HCL. Those little bottles are pretty leak proof, but the occasional escaped drop still wrecks a shirt from time to time. Concentrated HCL is just too dangerous to have in your pocket. The other things are useful if you are on a project with specific needs (for example if you are looking for oxide zinc), but otherwise, the mineral properties are enough for me to raise suspicion and then test for certain at the lab.

@@GeologyUpSkill I usually use a double or even triple barrier "system" with higher concentrated HCl. But because of that i only use it very occasionally 😅

The host skarns, mantos and carlin style deposits. They are some of the best gold deposits :)

If it is a mineral, I recommend mindat.org their website has an excellent gallery of images for almost every mineral.

If you love karst topography, you must visit Laos and it's neighboring countries. The karst exposures are spectacular.

Great way to start making your own videos. I have a video on how to do that here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ENOslkR0BwI.html

@@GeologyUpSkill OK，I will try.

If you turn on "Closed Captions" in RU-vid, you will get auto generated subtitles. They are pretty good despite my Australian accent!

Better put some acid on it then. Perhaps it is carbonate altered!

@@GeologyUpSkill Hmmm...never thought about that. The white weathering rind on these basalts from Newfoundland seems to be caused by burial in acidic soil.

Next time I see some I will make a video.

That's a neat way to remember it!

That will work, particularly if you scratch the carbonate before applying it. And it won't burn a hole in your shirt!

Most of the ankerite I have seen is in hydrothermal veins and breccias. I might have a biased view since I tend to work on hydrothermal ore systems most of the time. As you say, colour is a very poor indicator of mineral species, particularly for carbonates. The most useful indicator l find for ankerite is that rapid development of an iron oxide surface stain after cutting.

@@GeologyUpSkill Essentially 100% of my presumed ankerites as very dark scalenohedral structures in geodes and other volcanic rocks scan in reflectance infrared as calcite. I can tell the carbonates apart in infrared. It takes very specific and rare conditions for me to see it. For example, the Moroccan black brecciated nodules. Typically in things like Midwest saddle rhomb structures in sedimentary geodes and no place else.

My interest is volcanic agates, jaspers, and opals. These map into ore occurrences all the time. If it is banded agate with silver then I study it as banded agate. For example, other vein lode outcrops of the Calico silver deposits. Given that, the lack of ankerite was very startling to me, and the absolute lack of dark calcite scalen and rhomb structures being ankerite is nearly absolute. My classification keys are for feldspars, all the silicas, the opals (more silicas of course), sulfates, phyllosilicates, the carbonates such that I see 13 species of opals including species like opal-BC (opal-beta-cristobalite) and mixed species like opal-BC-CT, opal-CTA, and so on. I can see mixed carbonates. The agates I call calcsilica rocks as the silica deposition is strongly related to alkaline conditions set up by carbonate occurrence. And if the acidic rocks are around, they react with carbonates to form sulfates with the silica, so on a fine mm scale still form in alkaline conditions. For me, gossan caprocks are jasper occurrences. They occur in hydrothermal vents, along faults, fault offsets of water entrapment, etc, not dissociated from what ore geologists would hunt for. I just hunt them for specimens, not ore to crush and soak in acid, but the search is the same.