Niğde Calcite

Niğde calcite is a natural calcite mineral extracted from the Hıdırlık locality in the central district of Niğde Province, Türkiye, characterized by high purity and whiteness. It was registered as a geographical indication on 08.09.2022 under the Industrial Property Law No. 6769 and is protected under geographical indication rights. The registration process was carried out by the Niğde Chamber of Commerce and Industry.

Definition and Distinguishing Characteristics

Niğde calcite is the crystalline form of calcite, the primary mineral in carbonate rocks such as limestone marble and chalk, exhibiting a glassy luster colorless and transparent crystal structure. Its crystals form in rhombohedral and scalenohedral shapes. It has a wide range of industrial applications and is processed into various forms ranging from mosaic stones to micronized and nanometric powders. Surface-coated varieties are also produced.

Niğde calcite has three key distinguishing characteristics: grain size color and chemical purity. These properties determine the suitability of the product for specific applications. The color scale ranges from bright white to light gray while the calcium carbonate (CaCO₃) content varies between 80% and 99.9%. Contaminant elements such as iron magnesium and aluminum are present at low levels in calcite obtained within the geographical boundary. This contributes to higher whiteness and purity levels.

Chemical Composition Characteristics

The chemical composition of Niğde calcite is defined by high purity and low levels of impurities:

• Calcium carbonate (CaCO₃) content is 99.50%.
• Magnesium carbonate (MgCO₃) content is 0.30%.
• Iron oxide (Fe₂O₃) content is at a level of 0.005%.
• Silicon dioxide (SiO₂) content is 0.10%.
• Aluminum oxide (Al₂O₃) content is 0.05%.

Physical and General Properties

The physical structure and general properties that determine the usability of Niğde calcite are as follows:

• Density is 2.7 g/cm³ according to ISO 787-10 standard.
• Mohs hardness is 3.
• Refractive index is 1.59.
• Moisture content at factory outlet is 0.3%.
• pH value is 9.
• Linseed oil absorption for particles sized 5 microns is 15 g/100 g.
• Dop oil absorption for the same particle size is 28 g/100 g.
• Packaging density is measured at 1.00 g/mL.
• Whiteness value (L*) is 98.5%.
• Uniaxial compressive strength is 300 kg/cm².
• Solubility in water at 20 °C is 0.014 g/L.

Production Process

Niğde calcite is extracted from calcite deposits within the geographical boundary using drilling and blasting methods. It is loaded onto trucks by excavators and transported to a crushing unit. Depending on demand it is sold either in raw form or classified by sieves. Material with unsuitable color is manually or optically sorted on a triage belt.

Grinding operations are carried out in two main size categories:

• -40 micron: Jaw crusher → Hammer crusher → Ball mill → Screw conveyor → Air separator → Fan and filter → Product silo → Bagging
• 40–100 micron: Jaw crusher → Hammer mill → Separator → Bagging

Coating processes are performed in specialized facilities. Packaging is carried out using robotic systems where automated systems are available.

Geographical Boundary and Economic Contribution

Niğde calcite is extracted processed and packaged exclusively in the Hıdırlık locality of the central district of Niğde Province. It has long held a significant position in the regional economy.

Monitoring

The monitoring process is coordinated by the Niğde Chamber of Commerce and Industry. The monitoring authority consists of the Department of Mining Engineering at Niğde Ömer Halisdemir University the Niğde Directorate of Industry and Technology and relevant experts. Inspections are conducted at least once annually or as needed or upon complaint. Monitoring covers the suitability of calcite deposits the physical properties of the product and the correct use of the geographical indication mark.