Lithophysae from the Estérel

Siliceous structures formed in volcanic rock

A lithophysa is not a mineral species in its own right, but a structure formed within silica-rich volcanic rock. In the Estérel massif, lithophysae occur in Permian rhyolites. They consist of cavities or zones that are generally rounded or ellipsoidal and have been progressively lined or filled with silica deposits.

Chalcedony forms an important part of this filling and may be accompanied by crystalline quartz or minerals coloured by various oxides. Depending on the conditions of formation, a lithophysa may be almost completely filled or may retain an internal cavity. Its outer surface is often irregular, while the interior can display layers, colour contrasts or crystallised areas.

Choosing an Estérel lithophysa for a collection

When comparing several lithophysae, useful points to examine include their overall shape, the condition of the outer surface, the distribution of colour and the clarity of any visible internal structures. The outlines, chalcedony layers, possible quartz areas and contrasts between the different parts of the piece can all contribute to its visual appeal.

Size, weight and the overall balance of the specimen are also worth considering. The photos and videos allow each lithophysa to be viewed from several angles and help you choose the piece whose shape and characteristics best suit your collection.