Tarno is a dark grey to black limestone characterized by striking black linear patterns formed by ancient organic matter. These dark veins consist mainly of lignin and cellulose from plants, preserved at a time when fungi were not yet able to decompose such material.

The stone has an otolith structure, composed of small, rounded grains formed in shallow marine platforms similar to today’s Bahamas, where continuous wave action caused repetitive rolling and deposition. During lithification, the stone was subjected to slight heating, transforming the organic material into keratogene—an early stage in the formation of coal and oil—which became concentrated in thin, distinctive layers.

Tarno can be finished with a leathered surface, resulting in a very hard and refined black appearance with a rich tactile texture. When used indoors, the stone maintains its deep black color and visual depth. In outdoor applications, prolonged exposure to ultraviolet radiation may gradually turn the keratogene layers to a lighter grey over several years. Regular surface treatment or coating can help slow this natural aging process.

Due to its geological characteristics, large-format tiles may exhibit slight curvature. It is therefore recommended that suppliers carefully control flatness during production and installation. To accommodate potential movement, joint widths of 1 to 2 cm are advised.

Tarno Limestone is well suited for interior walls, feature areas, and architectural surfaces where natural depth, texture, and geological character are desired.”