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[Roger Warin]

And Paris Museums

[Roger Warin]

The vision of many gold nuggets saturates the eyes. At Sainte Marie, the monotony was broken by associating with the nugget a mineral whose general form was similar. This original idea was realized by the group Mineral & Gem. (MNHN Paris?).
The gold sample is thus highlighted by a remarkable mineral.
Not only are the shapes similar but, for contrast, the colors are complementary. Of course the color of gold is green in transmitted light.
The most breathtaking association is that of gold pseudomorphoses after pyrite compared with malachite on Chessy pyrite.

Octahedron showing a hollow-faced skeletal growth, this type is common to Chessy, and still has a complete pseudomorphose malachite.

In the same way, gold concentrated on the edges of the growing pyrite crystal at Bodaybo (Russia). Alteration dissolves pyrite. It remains the skeletal form where the gold was deposited.
It may be this comparison that gave the idea to the curator to present gold and a mineral.

In 2016, I had already seen several pseudomorphoses of gold after pyrite at Sainte Marie.

[Roger Warin]

My visit to the Sainte-Marie Show always ends with the visit of Alsatian wine cellars.
This sphere set with corks has a false symmetry, induced by ethyl alcohol.
My reports always end with the smile of this pretty Alsatian carved in the wood and presented on the screw of a press of bunches of grapes.
And finally, a stork on the top of a chapel. Life is sweet in Alsace.

[Gagat Minerals]

[Roger Warin]

Hi,
I think you were surprised by what I said. The lure of gold has been the downfall of many people.
Explaining the color of minerals is a difficult task without resorting to difficult theories for the amateur. This is certainly also the case for metals. Why is silver white like polished silver and why is gold yellow and copper red?
It all depends on the efficiency of the absorption of the light beam and its re-emission by reflection. Silver reflects light well according to all the wavelengths that compose it.
If there is an increase in the energy level, the efficiency of absorption decreases, as is the case for gold and copper. The reflectivity is reduced to the blue-green end of the spectrum and the metal appears yellow (gold) or reddish (copper). Gold and copper have low reflectivity at short wavelengths, and are preferentially reflected.
Gold can be beaten into gold leaf less than 100 nm thick, revealing a bluish-green color when light is transmitted through it. Gold is yellow, but not blue-green.

[Gagat Minerals]