Rare Earth Mineral Observations So Far

 

“Not that we needed all that for the trip, but once you get locked into a serious drug collection, the tendency is to push it as far as you can.” Hunter Thompson, Fear and Loathing in Las Vegas

My rare earth mineral collection stands at over forty specimens of at least 12 species, bought nearly entirely from Wendi (Ace) at Minerals Unlimited in Ridgecrest, California.

These do not include my radioactive minerals, although some of them cross over into the world of REEs.

 

Bastnäsite (Ce), a carbonate (bring your acid bottle!) rare earth mineral from Mountain Pass, San Bernardino, County, California. In association with limonite, barite, and calcite. According to the decades old label, the bastnäsite is primarily the tan material, the barite white, the calcite pink. Although Drew Barkoff says this is probably in error, his Mountain Pass specimen shows bastnäsite as pink.

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I bought these rare earth minerals about six months ago and eventually laminated all of the paper labels. I then got two inexpensive plastic cases at Home Depot. I am only now starting to go over this reference collection.

These are nearly all hot and I usually keep them outside because of that. I wash my hands after handling but I do not wear gloves.

I’m checking for UV right now and coming to an interesting conclusion. That syenite, an intrusive igneous rock, is something like black sand with placer gold. Black sand does not guarantee that you will find gold, but it is a sign of hope. Syenite is a sign of hope for prospecting rare earth minerals.

My reference syenite (melasyenite) specimen is below.  It resembles a granitic rock.  It glows red and black under SW with an 18 watt lamp.

This hopeful indicator revealed itself as I put each specimen under UV. Only one specimen lit up by itself but a red glow emerged from the matrix of several specimens. I wasn’t going to note that at first, rather, I only wanted to see if a mineral reacted itself. But I changed my mind as I went along.

At least ten of the specimens I looked at have syenite as a matrix or is part of their matrix. When syenite isn’t listed on a label but the rock glows red, invariably syenite will be listed as host or part host at Mindat. I still have thirty or so rocks and minerals to look at but this is an interesting trend.

I mentioned that the rocks were hot. Indeed, radiation seems a more sure way to help with decting rare earth minerals than UV. These two characteristics are sometimes shared, of course, both forms of radiation, but these minerals are far more easily detected with a geiger counter than a UV lamp. Also, as mentioned above, when the geology of an area suggest carbonate REE’s, bring along your acid bottle.

To know what one has found in the field, though, a REE mineral must be identified by laboratory analysis. These minerals are too complex and too alike to be reliably keyed out by visual, mechanical, or chemical testing.

The syenite pictured above comes from Geological Specimen Supply. It’s one rock out of my rock reference collection, chiefly bought from that excellent company.

Of note is that rock was collected from the Mountain Pass Area in San Bernardino, County, California. That area is a rare earth mineral district. The mine owned by Molycorp there is the “Highest-grade REE mine in the world,” according to Drew Barkoff, Friend of The Book.

Here’s R.C.’s description of this syenite. He includes such information for every rock he sells. This should convince you to start your own reference collection of common and not so common rocks.

“Syenite is an uncommon coarse-grained intrusive igneous rock with the same general composition as granite, but with less than 5% quartz. The feldspar, dark pink to purple in this syenite, is microcline. Hornblende, aegirine, phlogopite and biotite occur in varying amounts, giving the outcrop a maroon cast and making the syenite darker than usual. Melasyenite, from the Greek melas for black, refers to the dark shade of this syenite.

“This syenite occurs in the Mescal Range in California, at Mountain Pass, where two composite syenite-shonkinite bodies are associated with the Mountain Pass carbonatite complex that contains the ore that is being mined for rare earth elements by MP Mine Operations. Melasyenite and shonkinite are both unusual igneous rocks.

“Syenite forms with the low degree of melting that occurs in a granitic parent rock in a subduction zone or in an area of thick continental crust. A low degree of melting releases potassium into the melt to produce orthoclase/microcline, with slower cooling producing microcline. A greater degree of melting would cause the release of calcium and sodium, the feldspar would become plagioclase, and a granite would form.

 

Sign put up by Molycorp to identify their claims in what they call a rare earths district.

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