Osmaneli Lefke Stone

Osmaneli Lefke Stone is a natural stone extracted by open-pit mining from a single quarry located in the Osmaneli district of Bilecik Province. Used as a building stone, it initially appears yellowish when extracted from the quarry but gradually oxidizes upon exposure to air, acquiring a greenish hue. No plaster-like surface coating is applied to its exterior. This stone has been used in the construction of numerous historical structures, including the Haydarpaşa Terminal and the Bebek Mosque.

Product Characteristics

The following are some technical properties of Osmaneli Lefke Stone:

• True density: 2680–2690 kg/m³
• Apparent density: 2320–2450 kg/m³
• Open porosity: 3.3–7.70%
• Total porosity: 8.70–13.70%
• Water absorption by weight at atmospheric pressure: 1.91–3.31%
• Uniaxial compressive strength: 90.0–95.0 MPa
• Bending strength: 11.0–12.0 MPa
• Bending strength after freezing: 13.5–14.0 MPa
• Wear resistance: 18.0–19.0 mm
• Shore Hardness: 50–51
• Density: 2.66–2.69 g/cm³
• Classification: Arenite group, Dott (1964)
• Schmidt hammer average value: 36 (in situ)

The stone, which is soft when first extracted from the quarry, hardens over time during processing and after installation in structures. Decorative finishes can be applied to its surface.

Production Method

The production and application of Osmaneli Lefke Stone involve the following stages:

• The stone is extracted exclusively from the single quarry located at the specified coordinates in Osmaneli district, using the open-pit system.
• A sorting and cleaning process is carried out on the quarry face.
• Blocks weighing 250–300 kg are cut using sawing machines and transported to processing areas.
• Depending on the intended use, the stone is cut into square or rectangular dimensions ranging from 30 cm to 1 m using stone cutting saws.
• Blocks can be easily extracted during quarry operations using simple drilling equipment.
• Surfaces to which the stone will be applied must be flat, smooth, and clean.
• During application, a thick-bed adhesive mortar, typically weighing 25 kg, is generally used. This cement-based mortar has reduced slip properties and is resistant to water, heat, and freezing.
• The mortar is mixed with 6–7 liters of water, allowed to rest, then spread onto the surface using the flat side of a trowel and textured with the notched side.
• The same mortar is applied to the back surface of the stone, pre-cut to the required dimensions, and then affixed to the application area.
• After placement, the stone is gently struck with a rubber mallet to ensure proper contact, and then left to cure.

No plaster-like coating is applied to the exterior surface of the stone. Over time, its surface oxidizes, developing a greenish tone and acquiring a hardened structure.

Geographical Boundary

The geographical boundary of Osmaneli Lefke Stone encompasses the natural stone deposit located in the Osmaneli district of Bilecik Province, defined by the coordinates: 40.343943–30.037638, 40.343828–30.040341, 40.341390–30.037230, and 40.341415–30.042122.

Due to the stone’s long historical heritage and its significant role in the district’s economy, all production stages must be carried out strictly within the designated geographical boundary to preserve its recognized reputation.

Monitoring

Monitoring is conducted by a three-member oversight body coordinated by the Osmaneli Municipality, with participation from the Osmaneli Sub-governorship, the Osmaneli District National Education Directorate, and one expert appointed by the Osmaneli Municipality.

Monitoring is carried out annually on a regular basis, and may also be conducted at any time if deemed necessary or upon complaint.

The oversight body verifies the following aspects:

• That the natural stone is extracted exclusively from the quarry in Osmaneli district.
• Compliance with the established production method.
• Conformity of the product with its specified characteristics.
• Proper use of the designation Osmaneli Lefke Stone and the official emblem.

Any non-conformities identified during monitoring, along with the necessary corrective measures, are communicated to the inspected individual, institution, or organization. The oversight body may consult or procure services from experts employed by public or private institutions. The entity registered for the product’s protection is responsible for pursuing legal procedures to safeguard its rights.