Sillar

Sillar is a type of volcanic rock that is white or light gray in color and composed primarily of ash that has been fused and solidified. It is formed from volcanic eruptions where large amounts of ash are ejected and then subjected to heat and pressure, often through geothermal activity or subsequent lava flows. This process causes the fine particles of ash to coalesce and harden into a relatively lightweight, porous stone.

The most famous source of sillar is the area around Arequipa, Peru. The distinctive white buildings in the city, including its historic churches and homes, are constructed from blocks of sillar quarried from nearby volcanoes such as El Misti. This material has been used for construction for centuries, contributing to Arequipa's unique architectural character.

Sillar is known for its ease of carving and its relative lightness, making it a popular building material in its region of origin. While aesthetically pleasing, its porosity can make it susceptible to weathering in certain environments. Despite this, its historical and cultural significance, particularly in Arequipa, remains considerable. The mining and use of sillar is a traditional craft that continues to be practiced.