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Fluorescent Chalcanthite with Antlerite, Brochantite-MDO2 and Shungite(1) - Dongchaun, China/荧光胆矾

An unusual find in Dec 2021, hard to say to be beautiful but strange enough indeed. As chalcanthite is a simple copper sulfate mineral, there are many famous localities for it like AZ of US or copper mining area of Poland, in China, Qinglong County is also a famous locality, but we never heard if any chalcanthite glows.

Cu(II) is a common quencher as none of Cu(II) minerals glows if I remember well (different from Cu(II), Cu(I) is usually an activator, e.g. marshite). But, these chalcanthites does, perhaps some antlerites also.

SW-275 nm fluorescence

3.8 x 2.4 x 1.8 cm

White light (5300K)

Blue to light blue - Chalcanthite mixed with antlerite

Black - Shungite(1)

Green dots - Brochantite-MDO2

Yellowish green(at top) - Evansite

LW-365 nm fluorescence

FOV~4.46 mm

White light (5300K)

Blue to light blue - Chalcanthite mixed with antlerite

These samples are from a new and active locality of Dongchuan District, Kunming City, Yunnan Prov., China, which is famous for its extremely cute veszelyites. Chalcanthite samples are pretty fresh to this area. By miner said, the detailed locality is from Sanguozhuang Pb-Zn Mine, actually an illegal mining area. As a part of Dongchuan Cu ore field, copper mining activities have been lasting for hundreds of years here.

Sanguozhuang is located at the red star

There are analyzing works

Here we did some analysis work. Firstly, we need to figure out what they are, by SC-XRD and Raman. SC-XRD analysis gives its cell parameter as a=5.9580(5) Å,b=6.1140(6) Å,c=10.7212(9) Å,α=77.452(8)°,β=82.384(7)°,γ=72.740(8)°,V=363.08(6) Å3 by P-1 space group, it hits chalcanthite completely, also Raman.

Crystal structure of analyzed chalcanthite

Raman spectrum of analyzed chalcanthite

And some areas show pare blue received different Raman spectrum from chalcanthite, peaks between 3000-4000 cm-1 (this is the "water" range) are changed into two sharp peaks at 3488.6 cm-1 and 3579.4 cm-1, it means the tested crystal has two sets of OH- group. And it final fits recorded antlerite's Raman spectrum pretty well.

Raman spectrum of analyzed antlerite

Secondly, for figuring out what causing its fluorescence, we did some further works.

Geiger counter gives about 0.45 μSv/h when the Geiger tube put closed to a 8 cm sample, so, it's obvious radioactive.

SEM-EDS result shows it contains minor Uranium. Also confirms evansite, strictly speaking, it confirms the yellowish green part as an Alumium phosphate mineral.

EDS spectrum of chalcanthite

(Peak at abt 2.1 keV is related to Au coating)

EDS spectrum of evansite

(Peak at abt 2.1 keV is related to Au coating)

EDS gives results as both evansite and chalcanthite (also antlerite perhaps) contains about 0.5 wt% of Uranium, but as SEM-EDS is semi-quantitative test, the content is for reference only.

And PL at 325 nm also gives very typical spectrum that show its fluorescence is caused by uranyl ions (UO2 2+), peaks at 498 nm, 519 nm, 542 nm, 567 nm and 597 nm are all classified to UO2 2+.

PL spectrum of Chalcanthite (325 nm laser, 299K, 5s/2t)

Easy reading

Chalcanthite Cu(SO4) · 5H2O

Antlerite Cu3(SO4)(OH)4

Brochantite-MDO2 Cu4(SO4)(OH)6 A rare polytype of Brochantite, different structure with common Brochantite-MDO1

Shungite a kind of noncrystalline carbon

Evansite Al3(PO4)(OH)6 · 8H2O

沈洪涛/Hercule Shen

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