Luminescence, fluorescence and phosphorescence of minerals

EVANSITE

Chemical Formula: Al₃(PO₄)(OH)₆ 6H₂O (?)

Familly: Phosphates, Arseniates, Vanadates

Status: IMA-GP

Crystal System: Amorphous

Mineral for Display: No

Associated names (luminescent varieties, discredited names, synonymes etc.): BOLIVARITE,

Luminescence:

UV Type	Main color	Intensity	Observation Frequency

Long Waves (365nm):	Greenish white
Mid waves (320 nm):	Greenish white
Short Waves (254 nm):	Yellowish Green

Other colors LW:	Bluish White , Yellowish White ,
Other colors MW:	Bluish White , Yellowish White ,
Other colors SW:	Bluish White , Greenish , Greenish white ,

Daylight Picture

CALCITE (improperly labeled EVANSITE), Richelle, Visé, Province de Liège, Belgique;
Daylight
Col. G.Barmarin; Photo: G. Barmarin

Long Waves Picture (365nm)

CALCITE (improperly labeled EVANSITE), Richelle, Visé, Province de Liège, Belgique;
UVLW
Col. G.Barmarin; Photo: G. Barmarin

Short Waves Pictures (254nm)

CALCITE (improperly labeled EVANSITE), Richelle, Visé, Province de Liège, Belgique;
UVSW
Col. G.Barmarin; Photo: G. Barmarin

Phosphorescence (in the common meaning of the term) seen by naked eye:

No Data

Comments:

Rik Dillen and Axel Emmermann have shown (2021) that evansite samples from a deposit along a road in Richelle (Belgium) and presenting a globular crust facies on a schistose rock (see picture), sold for decades on Belgian mineral fairs with the label evansite, are in fact mainly made of calcite (see also Philippo, 2019). An analysis by Raman spectrometry on several points of a sample of this type in my collection unambiguously indicates the presence of calcium carbonate and not of evansite (aluminum phospate). The fluorescence is also quite similar to that of many calcites.

In some amateur collections, other samples of Richelle's evansite on a completely different matrix (breccia) also appear to be fluorescent as mentionned by Van Tassel in his paper (1959, see bibliography), but their exact nature needs to be confirmed (green crandallite?). The morphology of the samples described by Van Tassel in the gray breccia of Argenteau (white to gray nodules not exceeding one millimeter but showing fuorescence in blue-white tints) still does not correspond to these samples. In the book 'Les minéraux de Belgique' (Fransolet et al., 1974) evansite is not on the list of minerals from the locality of Richelle, but that of Argenteau (Philippo, 2019).

The fluorescence of real evansite samples from Belgium therefore remains to be studied.

Main Activator(s) and spectrum:

Most Common Activator: (UO₂)²⁺ (Uranyl ion) as impurities

Other activators: Organic impurities ,

Peaks in the spectrum (nm):

Organic impurities: Broad band centered around 500-550nm (not related to evansite but calcite from Richelle)

Col. G. Barmarin; Spectre: G. Barmarin

Comments on activators and spectra:

The spectrum shape of classic samples from Richelle combined with strong phosphorescence lets think that the fluorescence is due to organic impurities (but finally those samples seem to be only common calcite!);

Green fluorescence is clearly due to uranium in impurities (see bibliography).

Best Locality for luminescence(*):

Richelle, Visé, Liège Province, Belgium (yellowish-white SW+LW labeled as evansite but in fact most samples are mainly calcite without the presence of evansite);
Argenteau, Visé, Liège Province, Belgium (yellowish-white SW+LW labeled as evansite but in fact most samples are mainly calcite without the presence of evansite);
Železník (Vashegy), Sirk, Revúca Co., Banská Bystrica Region, Slovakia (ex Gomor, Hungary LT);
Porto, Porto District, Portugal (green SW);

(*)Data are not exhaustive and are limited to the most important localities for fluorescence

Bibliographical Reference for luminescence:

The Henkel Glossary of Fluorescent Minerals, Dr. Gerhard Henkel, Published by the FMS, 1989 ,

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Database of luminescent Minerals