The Fluorescent Quartz from La Sassa

Aggiornato il: apr 1


Sample of Quartz exposed to short wave ultraviolet rays.


Quartz of La Sassa, if exposed to ultraviolet rays, both long wave (UVLW) and short wave (UVSW), shows an intense yellow fluorescence (see also article Fluorescent Minerals).


The area to search is located just before reaching the town of La Sassa in correspondence with the small cemetery.


The works to make the road moved a large amount of rock which was partially poured down the slope. The specimens are still located just above the cemetery and in the adjacent agricultural field.


This area is located on the edge of the geothermal area of Larderello. The chemical elements suspected of being fluorescence activators are:

– (UO2)2+, Tb3+, Eu3+, Dy3+, Sm3+, Ce3+ yellow fluorescence of the quartz;

– Sm3+, Dy3+, Eu+3, Mn2+ red fluorescence of the calcite.

(from LUMINESCENCE SPECTROSCOPY: A POWERFUL TOOL FOR STUDYING HYDROTHERMAL MINERALS. THE EXAMPLE OF REE-DOPED SILICA PHASES IN A SINTER DEPOSIT CLOSE TO LARDERELLO GEOTHERMAL FIELD, ITALY – Dallegno et Al. 2013)







The same activating elements can also be found in calcite which however has a variable color between orange and violet (as seen in the image below in the upper part of the sample).



A common practice when rocks from this area are found is to acidify the whole sample with muriatic acid (10% -30%) so as to dissolve the calcite and only quartz remains.


Warning! Muriatic acid is highly dangerous and, if you are an underage, it should always be used by an adult. In general, it should be handled outdoors, with eye, face and skin protection, because sometimes the reaction can also be very violent and unexpected.


The samples seen in the photos have been treated in this way and for this reason calcite is almost non-existent.

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