Niğde calcite is a natural calcite mineral extracted from the Hıdırlık area in the central district of Niğde, Türkiye. It is characterized by high purity and whiteness. The product was registered as a geographical indication under the "trademark of origin" on September 8, 2022, in accordance with the Industrial Property Law No. 6769, granting it geographical indication protection. The registration was carried out by the Niğde Chamber of Commerce and Industry.
Description and Distinctive Features
Niğde calcite is the primary mineral in carbonate rocks (limestone, marble, chalk) and occurs as colorless, transparent crystals with a glassy luster. Crystals are formed in rhombohedral and scalenohedral shapes. It has a wide range of industrial applications, from mosaic stones to micronized and nanometer-sized powdered products. Surface-activated (coated) types are also produced.
The three main distinguishing features of Niğde calcite are grain size, color, and chemical purity, which determine its suitability for various applications. The color ranges from bright white to light gray, and calcium carbonate (CaCO₃) content varies between 80% and 99.9%. Contaminants such as iron, magnesium, and aluminum are low, enhancing the whiteness and purity of the product.
Chemical Composition
- Calcium carbonate (CaCO₃): 99.50%
- Magnesium carbonate (MgCO₃): 0.30%
- Iron oxide (Fe₂O₃): 0.005%
- Silicon dioxide (SiO₂): 0.10%
- Aluminum oxide (Al₂O₃): 0.05%
Physical and General Properties
- Density (ISO 787-10): 2.7 g/cm³
- Mohs hardness: 3
- Refractive index: 1.59
- Moisture content at factory exit: 0.3%
- pH value: 9
- Linseed oil absorption (5 μm sample): 15 g/100 g
- DOP oil absorption (5 μm sample): 28 g/100 g
- Packing density: 1.00 g/mL
- Whiteness (L*): 98.5%
- Uniaxial compressive strength: 300 kg/cm²
- Solubility in water at 20 °C: 0.014 g/L
Production Process
Niğde calcite is extracted from calcite deposits within the geographical area using drilling and blasting. Excavators load the material onto trucks for transport to the crushing unit. The raw calcite is either sold as-is or classified using sieves. Pieces that do not meet color standards are removed manually or via optical devices.
Grinding is performed in two main sizes:
- <40 μm: Jaw crusher → Hammer crusher → Ball mill → Screw conveyor → Air separator → Fan and filter → Product silo → Bagging
- 40–100 μm: Jaw crusher → Hammer mill → Separator → Bagging
Coating operations are carried out in specialized facilities. Packaging is automated and, where available, performed using robotic systems.
Geographical Boundary and Economic Contribution
Niğde calcite is extracted, processed, and packaged exclusively in the Hıdırlık area of Niğde central district. The product has been economically significant to the region for many years.
Inspection
Inspections are conducted under the coordination of the Niğde Chamber of Commerce and Industry. The inspection committee includes experts from Niğde Ömer Halisdemir University, Mining Engineering Department, Niğde Provincial Directorate of Industry and Technology, and relevant specialists. Inspections are carried out at least once a year, or when necessary or upon complaints, focusing on deposit suitability, physical properties of the product, and correct use of the geographical indication mark.
