Old vanadinite crystals from Berta Quarry (Barcelona, Catalonia)

 Vanadinite is a lead chlorovanadate Pb₅(VO₄)₃Cl, which belongs to the hexagonal system, and is formed as a secondary mineral in the oxidation zone of lead deposits in relatively arid climates, because of the alteration of sulphides and silicated rocks containing vanadium. It can also be formed in sedimentary deposits rich in fossilized organic materials, such as algae.

Vanadinite belongs to the Apatite Group and is the vanadium analogue of mimetite Pb₅(AsO₄)₃Cl and pyromorphite Pb₅(PO₄)₃Cl. In nature we could find compositional series between mimetite, pyromorphite and vanadinite.

It is a very characteristic mineral of the lead-vanadium mines those were exploited south of the Atlas, near Midelt, in Morocco. Moroccan specimens are highly prized by collectors due to the great aesthetics and intense colour, between red and orange, and even yellow.

Pedrera Berta in 2011. Photo Joan Rosell.

At the end of the 1980s, at the well-known Pedrera Berta (Berta Quarry) among collectors (a quarry located between the municipalities of El Papiol and Sant Cugat del Vallés, Barcelona, Catalonia), various specimens were collected containing small red to orange crystals disposed on a matrix formed by small and brilliant hyaline quartz crystals, with galena and pyrite. Some collectors erroneously identify them as orpiment (As₂S₃), very similar in colour.

Red to orange vanadinite on pyrite and quartz. Size: 3.5 x 2.5 cm. Ex-coll. Manchion. Photo and coll. Joan Rosell.

Vanadinite on pyrite. FOV: 2 cm. Ex-coll. Manchion. Photo and coll. Joan Rosell.

At that time, various analyses of these crystals were carried out by Dr. Joan Viñals (professor of Chemistry at the Universitat de Barcelona). Results indicated that it was this species: vanadinite. A posteriori, no more specimens have been collected in situ. We would have to check old mineral collections to find these specimens.

Some of us already had pieces acquired in the 90s, that allowed us to correctly determine specimens we had collected in this Catalan mine during these years.

We have analysed some of these vanadinite crystals again and we have been able to verify what Dr. Joan Viñals had already indicated, but also we have observed the presence of phosphorus, and minor arsenic, replacing vanadium in the structure of the crystals, which seems to indicate that they are mainly compositionally in the vanadinite-pyromorphite series.

Vanadinite (white) on quartz (grey). SEM photo by Joan Rosell.

The Berta samples appear as well faceted crystals, sometimes complex, showing the hexagonal prism truncated by faces of the dipyramid and with quite developed faces, sometimes, of another dipyramid of a different order.

Prismatic vanadinite crystal on quartz. FOV: 3 mm. Photo and coll. Joan Rosell.

Motic PlanApo 5x ELWD with stacking.

Vanadinite crystals and pyrite. FOV: 5 mm. Photo and coll. Joan Rosell.
Motic PlanApo 5x ELWD with stacking.

Vanadinite crystals and quartz. FOV: 1 mm. Photo and coll. Joan Rosell.
Motic Objective 10x with stacking.

 Currently the Pedrera Berta is inactive, access is strictly prohibited and the collection of specimens in this classic quarry is not feasible. Although the project that wanted to reuse the quarry as a landfill for inert waste was stopped, the impossibility of accessing it means that we are losing information about more minerals species that could still be collected there.