FMF - Friends of Minerals Forum, discussion and message board

[Roger Warin]

Exceptional fine Crystal of Jordanite from the Lengenbach Quarry, associated with other rare sulfosalts.

[Roger Warin]

Hessonite, a gemological term, belongs to the grossular garnet group. While most grossular garnet is green, the hessonite variety typically has a vivid orange-brown color.
It’s one of the nine planetary gemstones ! Where’s Pluto ?
Hessonite is typically associated with diopside (a calcic clinopyroxene) in the Val d’Aosta (Italy).

[Roger Warin]

Gwindel quartz or twisted quartz.

Crystalline individuals are associated according to a sub-parallel growth. There is a more or less a slight offset at each step.
The “c” axis of diverse individuals is parallel to the base. The twisted group develops along an "a" axis perpendicular to the "c" axis.
At each addition of an individual, there is a slight position shift that will create spin. They are not twinned. The rotation can be done right or left with the same probability.

[Roger Warin]

Gwindel

For the most spectacular Gwindels, the edifice can be quite high compared to the elongation of individuals.

[Roger Warin]

Sugar habit…
Also worth mentioning is that individuals can be more or less fine, as shown in the profile of the various apexes. At the limit, can be achieved even continuity, apexes blending then one curved edge, since there rotation of the construction. Light reflections show the torsion of the common face to the whole group. Thus talk of semi-closed or fully closed Gwindel. The French cristalliers kindly referred to these as "sugars" they form. True, they also suck them to clean on the summits ...
With the profile of the group, one can deduce the chirality.

[Roger Warin]

Kyanite – Staurolite epitaxy
Pizzo Forno, Tessin, CH.

I admit I do not see on the picture that famous epitaxy of staurolite on blue kyanite. Are these the two aligned crystals near the center of the photo?
In this epitaxy, the cleavage plane (100) of kyanite roughly coincides with the cleavage plane (010) of staurolite. (Friedel 1926).

[James Catmur]

Thank you Jordi and Roger - great information and photos

[Roger Warin]

Morganite
Morganite is a pink orange variety of beryl containing lithium and cesium.
I do not know why Morganite is a flattened variety of beryl.
Is morganite not elongated along the c axis, because of Cs ???
Pezzotaite, a similar mineral species with Cs, is not elongated too.

[Fiebre Verde]

Roger,
I have seen the emerald specimen featured in your photo Emeraude_00356_R in various shows prior to Sainte-Marie. Too good to be true!
Its price keeps going down show after show.
Gérard

[Roger Warin]

Gérard,
I do not know the price of this emerald. I was not interested in it. Possible gluing are not shown on a picture.
Roger.

[Roger Warin]

Gold from Alps.

The site of La Gardette was discovered by cristalliers in the early eighteenth century. It has been well operated for trade crystals from its beginning. Subsequent research has been rather unsuccessful.

[Roger Warin]

Gold

[Roger Warin]

Perovskite.

Perovskite is calcium titanate. Perovskite, black or reddish-brown color, has a metallic appearance. Although made of relatively light elements, the density is 4.0. Its modern applications are developed. They involve superconductivity, magnetoresistive and ionic conductivity. The ferroelectric ceramics according built structure are now very important and occur for example in the photovoltaics (solar cells with high efficiency) and fuel cells.
In addition, perovskites are among the minerals that will withstand very high pressures and temperatures, as in the Earth's mantle at very great depths, to the contact of the nucleus (where it undergoes deformation in post-perovskite). The perovskite was described in 1839 by the German mineralogist Gustav Rose from samples from the Urals, and dedicated to the Russian mineralogist Perovski (1792-1856).
A nice destiny for a simple mineral.
Rare specimen.

[Roger Warin]

Quartz

more traditional

[Roger Warin]

Quartz