Large and spectacular column-peana. France, ca. 1905. Agate.

Large and spectacular column-peana. France, ca. 1905.
Agate.
Measurements: 107 x 44 x 48 cm.
This octagonal column is defined by its clean, emphatic lines. It is made entirely of agate, a material which is not a specific mineral, but a group of micro-crystalline varieties of quartz (silica). In reality, they are varieties of chalcedony that present bands of different colours with little contrast. The difference in colours appears because in each zone the structure and the number of inclusions in the chalcedony varies, thus changing its properties. Agate is found in volcanic rocks that vary in size from millimetres to several metres. It is characterised by a series of concentric bands of similar colours, opaque and translucent, reminiscent of a tree trunk cut in a circular pattern. It can take many forms and comes in many varieties. It is a hard rock and resistant to chemical reagents. The most important agate deposits are found in the United States, Brazil, Artigas department in Uruguay, Argentina, India and Madagascar.