Oltu Stone

Oltu Stone is a valuable mineral extracted from the Oltu district of Erzurum and also known as "Black Amber." This stone forms within sedimentary layers, appearing as lens-shaped bodies several centimeters thick within marl beds that are 70–80 cm thick and of Neogene age. These lenses, composed of marl and clay, have fractured due to tectonic movements. Oltu Stone is typically black in color but can occasionally be found in brown, gray, and greenish tones. When extracted, the stone is soft but hardens upon exposure to air. This ease of working makes it unique for the production of ornamental items.

Physical and Chemical Properties

One of the most distinctive features of Oltu Stone is its structure: soft when extracted from underground, yet hardening upon contact with air. Thanks to this property, it can be easily shaped and carved by skilled artisans. Oltu Stone becomes electrically charged through friction and attracts light objects. For this reason, it has been attributed mystical significance throughout history and regarded in some cultures as a protective amulet against the evil eye. Its hardness on the Mohs scale is 3, and its specific gravity is 1.26.

Chemically, Oltu Stone contains 77.95% carbon and has a calorific value of 8,064 kcal/kg. Its crystalline structure is amorphous, and its chemical formula is denoted as C (carbon). When exposed to air, it ignites and burns, and it also becomes electrically charged through friction. The smoke produced during combustion was historically used in ink production. Additionally, the high gloss achieved when the stone is polished is one of the main reasons it is preferred for jewelry and accessory manufacturing.

Extraction and Processing

Oltu Stone is extracted by hand from small underground mines known as "galleries." After extraction, the stone is stored underground to prevent premature hardening. When needed, it is removed from the soil and carefully worked by artisans. Extraction is labor-intensive and typically done by manual digging. Stones obtained from gallery mines are carefully protected to avoid surface cracking and exposure to air.

To achieve a smooth surface during processing, the stone undergoes polishing. Materials such as polishing machines, wood charcoal, chalk, oil, and cloth are used in this process. During polishing, the stone’s surface is rendered smooth, revealing its natural luster. Polished Oltu Stone acquires an aesthetic appearance.

During processing, foreign materials and cracks within the stone are meticulously removed with great skill. Oltu Stone is fractured and chiseled into small prismatic shapes using a chisel on a wooden log, with care taken to minimize waste. Polishing is generally carried out using polishing machines, resulting in an extremely glossy surface.

Oltu Stone processing (Anadolu Agency)

Applications

Oltu Stone has a wide range of applications in the production of prayer beads, jewelry, and ornamental objects. In particular, its smooth and glossy surface makes it ideal for prayer bead manufacturing. Prayer beads made from Oltu Stone offer ease of handling and a pleasant tactile sensation. It is also widely used in necklaces, rings, earrings, bracelets, and various other decorative items. Additionally, it is carved with traditional Anatolian motifs to produce artistic pieces and souvenirs. This stone, unique to Erzurum, is both a source of livelihood for the local population and a cultural symbol.

Oltu Stone ring (Anadolu Agency)

Oltu Stone prayer beads (Anadolu Agency)

Geographical Indication and Protection

Oltu Stone was officially registered as a "Geographical Indication" on 27 November 2015. The registration, carried out by the Erzurum Oltu Chamber of Commerce and Industry, defines the geographical boundaries of this stone as exclusively the Oltu district of Erzurum Province. This designation ensures that Oltu Stone can only be extracted from this region and that its original characteristics are preserved. The geographical indication safeguards product quality and guarantees fair compensation for producers. Regular inspections are conducted under the coordination of the Oltu Chamber of Commerce and Industry, with contributions from the Oltu Vocational School of Atatürk University.