Carnotite Options

[Clodhopper]

Does anyone know if carnotite is found near the Baby Doe mine in Leadville?

Thank You.

[swizz]

Mindat doesn't show any recorded occurrences near Leadville, but that doesn't necessarily mean it hasn't been found near there. There are definitely occurrences in Colorado.
Here's the Mindat link. If you scroll down you can use the interactive map. Mindat Carnotite

[Clodhopper]

Thank You. I picked up a rock there last summer (we live in Missouri) with a yellow "dust" on it that sure is a possibility, at least to my non-geologist mind.

[fenixsmom]

If it smells like rotten eggs its just sulfur!

[Woody]

Hi Clodhopper,

Limonite is a possiblity for your find. It is fairly common and normally has a Yellow or Orange dust on it. By chance can you send a picture?

Try looking Limonite up and see if it fits, Woody.

[swizz]

I'd also love to see a pic or two if you have them Clod.

[MikeS]

Colorado Carnotite is mainly found near the leyden coal mine (Jefferson County) and in the Uravan Mineral Belt (Mesa, Montrose and San Miguel Countites) I have not seen any reports from outside those areas.

......I missed the link that swizz posted for mindat. It looks like there is several other reports.

[Coalbunny]

My question is, why do you suspect it to be carnotite? First, carnotite is radioactive. Have you checked for the radioactivity? Second, carnotite is a "secondary replacement mineral", i.e. a breakdown from other uranium/vanadium ores. Just like rust is for iron, in fact. That is dependant on the valence level of the primary minerals.

I will say that you will not find any carnotite in the Leadville area that I am aware of. However, there has been reports of carnotite in the Trout Creek pass area. I am not aware of to what extent that was found there, or when. One of the general locations of carnotite and other secondary replacement U/V ores is the Morrison formation of Jurassic age, as well as in the Chinle, and Moenkopi formations as well, IIRC. really it can occur anywhere you have uranium/vanadium ores oxidized, though it really is more dependent on the specific ores and conditions as well.

And now my few brain cells I have left are starting to overheat...lol! I don't know that stuff anywhere near as much as I used to. So I could be wrong. About some of it.

Most importantly- radiation. Get a geiger counter and check the specimens. no radioactivity, extremely unlikely chance it's carnotite.

[GeoMatt]

There are occurrences of both uranium and vanadium in the Mosquito District, and specifically in the vicinity of London Mountain - London Syncline area. I don't have a reference that list specific mineral species though. Carnotite is generally associated with sedimentary uranium desposits, however I have seen in it volcanic settings as well. As others have stated, I would tend to think limonite. Post up a pic so we can look at it!

[Coalbunny]

True, GeoMatt. Even on the other side of Mosquito Pass along Birdseye gulch traces of U&V were present and a history of V ores at two of the mines noted. It is secondary replacement mineral, so it'll occur in a lot of places where you have U & V present. Though it can also become tyumiminite, depending on the molecular calcium and potassium concentrations

As for carnotite occurances in Colorado, you can find it in a lot of places, particularly in mining districts such as Rifle Gap, Maybell, Slick Rock, Uravan, Monogram, Gateway, amongst others. I have specimens from those sites, not counting Slick Rock.

[Clodhopper]

Wow, lots of good info here, thanks. I will get a pic up soon. I do not have access to a g-counter. I did do a scratch and got yellow but a yellow crayon would do the same, LOL.

[Clodhopper]

My "carnotite" sample (?). About 5" long. A little more orange than pic shows.

[GeoMatt]

Though it can also become tyumiminite, depending on the molecular calcium and potassium concentrations

Tyuyamunite


Basically another member of the carnotite family - carnotite, tyuyamunite, margaritasite. All of them hydrous uranium-vanadate minerals, and generally have the same presentation in hand sample.

[Coalbunny]

My "carnotite" sample (?). About 5" long. A little more orange than pic shows.

What does the geiger counter say? And be careful because nearly all the land up there is private. There are patented claims every which way up there. So asking any of the locals can be dangerous.

If the GC gives normal background readings (IIRC up there about 150 CPM), I'd say limonite or a variety of oxidized ores. There's a lot of complex sulphides up there.

Tyuyamunite


Basically another member of the carnotite family - carnotite, tyuyamunite, margaritasite. All of them hydrous uranium-vanadate minerals, and generally have the same presentation in hand sample.

Yep!

[Clodhopper]

As I said above I don't have access to a geiger counter. From all the above info, best (simplest) guess is probably limonite.