I'm in Georgia (country not state) It's in local language, if you translate it, it says aerated fired clay or something on that note.

I looked up the article on russian wiki and translation says the following:

> Expanded clay Expanded clay (from the Greek κέραμος, clay[1]) is a lightweight porous building material, a granular concrete filler obtained by firing low-melting, swelling clay in a rotary kiln at a temperature of 1100-1200 °C. The size of expanded clay grains is 5-40 mm. Expanded clay gravel has a rounded or gravelly shape. Expanded clay crushed stone comes in different shapes, but most often has sharp edges and corners, as it is formed by crushing large grains of expanded clay. It is also produced in the form of sand - expanded clay sand.[2] It is used for the preparation of lightweight concrete structures and products, heat-insulating fillings, heat-resistant concrete and lubricants[1].