Finding rare earth minerals

[darshevo]

Admittedly this question is aimed mostly at Rick, but I of course welcome insight from all

Last summer my main hobby was chasing down abandoned mines. I checked out some great locales and burned a ton of fuel. All I ended up to show for it were some really nice ore samples, enough rocks for a dozen rock gardens and some great times with friends and family (the best find of all!)

One of the mines I located likely hasn't been touched in over 50 years. It is very well hidden and there is no indication anyone even knows it exists anymore. It was a copper mine in its day with trace amounts of gold and silver in the ore (information taken from an paper dated in the late 1800's) For its part I am thinking it may be a viable mine to reopen (due to the cost of copper today compared to the early 1900s when it was in its heyday)

Which brings me to my question (finally). I know that in times of rush miners will step over an abundant valuable ore to get to 'insert ore being hunted here'. I also know that a lot of abandoned and lost mines ended up that way in the era between WWI and WWII when prices made it unprofitable to continue operation. Since most of these mines that I know of have been untouched for 50-100 years it seems unlikely that anyone was looking for rare earth minerals when they were being mined. How does a person go about knowing where they 'should' be? Is there some geological hints a person can use? Is it a very specific set of circumstances that allows them to form thus making their locations easy to locate (from a geological stand point). There are areas not far from where i live where Uranium was mined at one time, as well as on an Indian reservation north of town that I can get access to through friends I have who live there.

Any thoughts or direction would be greatly appreciated

-Lance

 

[Richard36]

... it seems unlikely that anyone was looking for rare earth minerals when they were being mined. How does a person go about knowing where they 'should' be? Is there some geological hints a person can use? Is it a very specific set of circumstances that allows them to form thus making their locations easy to locate (from a geological stand point)

Any thoughts or direction would be greatly appreciated

-Lance

Good Questions.
I'll do my best to answer them.
I will have to go look through my books first though. I do not have that info memorized.
If you're lucky, I'll make a post with some sort of an answer later on.

Study time for me.
Am I getting paid for this one? lol!

All in fun, and meant to be funny.

Sincerely, Rick. "The Rock Man".

 

[turtlesteve]

I'm not sure I would agree with your comment that rare earths were overlooked 100 years ago - I would say they were MORE in demand at that time (in the US, at least). I'm familiar with many sites that were profitably mined in the early 1900's, but were abandoned later as applications switched to cheaper elements. In particular, thorium was in high demand for electric lights, rare earth elements (REE's) were used in lantern mantles, Zr in lighter flints. Th and Zr aren't rare earths, but often occur in the same deposits.

"Primary" (igneous) rare earth deposits are generally pegmatites that occur in the metamorphic cores of mountain ranges. Secondary deposits may be rare earth carbonates, or monazite (heavy sand) deposits. Generally REE do not occur in the same deposits as copper, silver, gold, etc. but there are some exceptions. I know of one pegmatite in S. Carolina that produced gold and REE, and one in N. Carolina that contains copper sulfides and REE.

Steve

 

[turtlesteve]

Sorry, missed your question about specifically finding REE deposits. I like to collect rare earth minerals so I can offer some guidance:

In pegmatites, rare earths occur predominantly in the mineral Monazite, which also contains a small percentage of Thorium. Other ore minerals (Samarskite, Pyrochlore, Betafite, etc.) also contain Thorium and Uranium. Therefore, the best bet for finding REE minerals is to visit pegmatite mines, and use a hand-held scintillometer. These are used like a geiger counter but work by a different mechanism and are much more sensitive. Heavy sand deposits can be found as you would find gold and black sands - by panning in places where you would expect heavy minerals to collect. These sands are brown in color (not black), are non-magnetic, and will be generally be slightly radioactive (again, a scintillometer would confirm this). I'm not that familiar with carbonate-type deposits but they are generally lower in concentration but larger in extent - my guess is these ores would be difficult to identify in hand specimen and would require a full assay.

Steve

 

[Oz]

Unless you are already an established miner with a serious budget at your disposal I would forget about rare earth elements even if you found them in quantity. Despite their name (rare earth) they are not really all that rare. They are however hazardous and expensive to refine from an ore. This is why all you hear in the financials of mining talks about China cutting off the rest of the world from their rare earth mining elements. Most countries have closed their rare earth mines and refining facilities as China was doing it on the cheap due to low labor costs and poor environmental controls.
Could China put the rest of the world in a bind? Sure, but only because it takes a few years to bring old mines and the refining back up and running again on all of the closed facilities that had shifted production to China to deal with the toxic waste at a lower cost.

Element samples however may be worth your effot selling to collectors.

 

[Richard36]

I don't feel like writing a book, so I'll just post my notes.

The three minerals listed below seem to be the ones available to us
here in Oregon and Washington, judging by rock type and mineral associations.

Aeschynite
Magmatic in Granitic Pegmatites, and Carbonates.
Zircon is the indicator mineral.

Monazite
Magmatic in Granitic and Alkaline (Basic) Pegmatites, Granites, Syenites and Carbonatites.
Hydrothermal in Alpine-Type Veins and Greisens. Metamorphic in Gneisses.
Apatite, Zircon and Zenotime are the associated minerals. (Indicator Minerals)

Eudialyte
Magmatic in Nepheline Syenites and their Pegmatites.
Coarse Grained Acid and Intermediate Igneous Rocks.
Aegirine, Nepheline, and Microcline are the associated indicator minerals.



*Acid Igneous Rocks
Over 65% total Silica and over 20% Quartz.
Granite, and all versions thereof.
Microgranite, Granophyre, Rhyolite, and Pegmatite.

*Intermediate Igneous Rocks (Coarse Grained)
Between 65% and 55% total Silica
Granodiorite, Diorite, Syenite, Nepheline Syenite, and Larvikite.
(Andesite and Dacite are fine grained.)

*Alkaline (Basic) Igneous Rocks
Between 45% and 55% total Silica, and less than 10% Quartz.
Gabbro, and all variations thereof.
Anorthosite


I hope that this has been helpful.

Sincerely, Rick. "The Rock Man".

 

[darshevo]

Thank you for the replies. Will give me some direction at this point. The area I was hoping would possibly be of interest is likely not going to be. I do have another area in mind now though, and it's even a bit closer to town.

As far as buying a scintillator is there anything to watch out for as far as brands, age, etc?

-Lance

 

[turtlesteve]

Lance,

Good hand-held scintillators cost >$1,000 new. I've bought 3 detectors on Ebay for between $200 and $300 each - two worked as received, one did not ($300 to repair). The factors I consider are detector type and display (panel meter vs. digital readout). Digital displays are preferred, they are more responsive and let you cover ground more quickly. Scintillators use a "crystal" which is anywhere from <1" in size to more than a foot in size. Sensitivity is proportional to size and the material used. NaI(Tl) is the most common crystal used, is very sensitive but very fragile (don't drop it!). I would recommend a plastic scintillator - they are less sensitive but are cheap and durable. Two of the units I bought were TSA surplus units (PRM-470, w/ ~3-4" plastic scintillator) that seem to be common on Ebay. These work quite well for mineral collecting. There are a couple available on Ebay now - item number 200568971951 - but with no guarantee that they still work.

If you want rare earth, U, and Th mineral specimens, this is in my opinion the best way to collect them. However, I agree with Oz - attempting to mine rare earth ores for the metal values would be a losing venture.

Steve

 

[Shecker]

Back in 1968, when I was spending the summer in the high mountains of Colorado, I discovered a huge porphorytic deposit rich in Monazite and other Rare Earth minerals. There was no interest in them then and there is no interest in them now, although that may change in the not too distant future.

As Oz says, they are expensive to mine and even more expensive to refine and process into useable materials. This next summer I may go back and take another look at that deposit.

Randy in Gunnison