Characterization of Stone from Jošanica Quarry and the Possibility of Its Application ^†

Abstract

This study presents a chemical and mineralogical analysis of stone samples from Jošanica quarry collected from three different locations—Field A, Field B, and Field C. Mineralogical analyses were conducted using XRD analysis. The analyses showed that calcite was the dominant mineral in most of the samples, while dolomite was significantly present in some of the samples. Chemical analysis revealed that calcium was dominant in samples 2 (Field B), 3a, and 3b (Field C), with only negligible amounts of magnesium. In contrast, samples 1a, 1b, and 1c (Field A) contained a significant amount of magnesium. Based on the MgCO₃ content, the amount of dolomite in the stone samples was calculated. The content of CaCO₃ in its bound form in dolomite was lower than that in the stone samples, indicating that CaCO₃ was present in another form. According to the dolomite content, samples 1a, 1b, and 1c (Field A) are classified as limestone–dolomite, while samples 2 (Field B), 3a, and 3b (Field C) are classified as limestone due to their high calcium carbonate content. The results of a mineralogical analysis confirmed the results of the chemical analysis.

1. Introduction

The term “rock” refers to a natural formation composed of minerals of a certain composition, structure, and texture produced as a result of various geological processes. Rocks are therefore composed of certain minerals. The mineral composition of rocks and the conditions of rock formation have a decisive influence on the application of the materials obtained from them. For example, the physical, mechanical, and other properties of building stone directly depend on the properties of the rock mass from which the stone is obtained [1,2].

Depending on the conditions and manner of formation, solid rocks, i.e., rocks used as building stone, can be divided into three basic groups: igneous, sedimentary, and metamorphic.

Magmatic rocks form during the crystallization of natural silicate melts—i.e., magma. The structure of deep igneous rocks is crystalline or porphyritic. The most representative examples of these rocks are granite, syenite, diorite, and gabbro. The texture of surface igneous rocks is fine-grained crystalline, but they often contain amorphous masses, such as volcanic glass. The most representative examples of these rocks are andesite, basalt, and diabase. The minerals commonly found in igneous rocks include quartz, silicates, and aluminosilicates: feldspar, mica, amphiboles, pyroxenes, and olivines [1,3].

Sedimentary rocks form on the surface of the Earth’s crust via the breakdown products of certain rock masses and the deposition of organic remains. Sedimentary rocks are divided into the following categories: 1. Pyroclastic rocks, such as tuffs; 2. Clastic sedimentary rocks, formed by cemented fragments, such as breccias, conglomerates, and sandstones; 3. Chemical sedimentary rocks, including some limestones, dolomites, bitumen, and travertine; and 4. Organic sedimentary rocks, formed from biological material, such as certain types of limestone, dolomite, and diatomaceous earth. The most important representative member of this group of rocks is limestone, a calcium carbonate raw material. The main mineral of limestone is calcite, with a chemical composition of CaCO₃, and dolomite (calcium–magnesium carbonate, CaCO₃·MgCO₃) is found as an admixture [4,5].

Limestone usually has a microcrystalline structure, but some varieties have large crystals. Metamorphic rocks result from the recrystallization and adaptation of certain rock masses under changed physical and chemical conditions. For this reason, the composition and structure of these rocks depend on the composition of the original rock from which the metamorphic rock developed. Examples include marble, quartzite, and gneiss. The structure of marble is predominantly microcrystalline [6].

The stone from Jošanica quarry falls under the category of sedimentary rocks. Based on detailed geological mapping, the geological structure of this deposit includes Permotriassic sediments, anisic limestones, limestones, pyroclastic formations of Ladinian age, and Quaternary sedimentary–deluvial formations [7].

Sedimentary rocks (from the Latin sedimentum) form in water or on land due to the accumulation of material resulting from the erosion of the lithosphere by mechanical or chemical weathering and organic processes. Sedimentary rocks also include carbonate rocks, such as limestone [8].

Limestone is a sedimentary carbonate rock composed primarily of the mineral calcite, though minor amounts of aragonite may also be present. There are different types of limestone, and they are classified according to their mineral composition and impurity content: dolomite, marl, silicified limestone, bituminous limestone, and others. Common impurities in limestone include dolomite, siderite, opal, chalcedony, quartz, clay minerals, iron oxides, and hydroxides. Based on the MgO content, i.e., the proportion of dolomite, limestone can be classified as follows [9]:

• Pure limestone, containing more than 95% CaCO₃ and less than 1.2% MgO;
• Slightly dolomitic limestone, containing less than 10% dolomite;
• Dolomite limestone, containing 10–50% dolomite;
• Calcitic dolomite, containing 50–90% dolomite.

The importance of limestone, in comparison to other rocks, is evident from the fact that its usage exceeds that of all other rocks combined. In the construction materials industry, limestone is used [10]

• For the production of building lime and Portland cement;
• For architectural stone production;
• For stone and stone aggregate production for hydraulic engineering, civil engineering, and railway construction;
• For the production of concrete aggregates (for buildings and prefabricated structures).

Products based on calcium carbonate raw materials of the required chemical composition are obtained in sizes of 3–5, 5–10, 20–24, 40–45, 60–65, 90–100, and 150–200 μm and used in the following areas: 1. the construction material industry, as filler for asphalt and in hydrocarbon mixtures; 2. the paint and varnish industry; 3. the animal feed industry; 4. the pharmaceutical and cosmetics industry; 5. the paper industry; 6. the rubber industry; 7. the glass industry; 8. the neutralization of acidic soils; 9. the production of mineral fertilisers; 10. the desulphurisation of SO₂ gas in thermal power plants and heating plants; 11. the production of PVC; and 12. other applications, including household preparation, such as in the manufacture of carpets, glues, plasters, etc. [11,12].

Carbonate fillers are used in all these branches of industry to improve the properties of the final product without requiring any chemical reactions with the other components. The limestone component used in the production of cement should contain more CaO than required by the saturation coefficient of the cement mixture [9]. Calcite, chalk, limestone tuff, marly limestone, etc., can be used as a limestone component. When marly limestone is used, it is preferable for the CaCO₃ to be in the form of finely dispersed calcite, with clay minerals present as an admixture. The presence of quartz grains complicates the production process but is not harmful. However, the additions of pyrite, dolomite, and gypsum in larger quantities is detrimental. Marl is, in fact, a natural mixture of calcite and clay minerals. The compositions of some marls completely correspond to the composition required for obtaining cement clinker, but these marls are rare in nature [13,14,15].

The SRPS B.B6.013 standard defines the quality conditions of crushed aggregate for the production of lime and sugar [16]. According to this standard, the quality limits for categories I and II are as follows: CaO, at least 54.35–53.23%; CaCO₃, a minimum of 97.00–95.00%; MgO, a maximum of 0.72–1.43%; MgCO₃, a maximum of 1.50–3.00%; CO₂, a minimum of 43.43–43.34%; SiO₂, a maximum of 0.80–1.00%; residue (R₂O₃), a maximum of 0.70–1.00%; and clay and humus impurities, a maximum of 0.5%.

According to SRPS U.F3.050, which specifies the technical requirements for terrazzo work, the following aggregate sizes may be used in terrazzo production: stone powder (0–1 mm), stone grit (1–2 mm), stone fines (2–4 mm), and coarse fractions of 4–7 mm, 7–10 mm, and greater than 10 mm [17].

The quality requirements for crushed aggregate used in metallurgy (in sintering, in blast furnaces, and in the Bessemer process for steel production, where the 80–120 mm fraction is used) are given in the SRPS B.B6.011 standard [18].

The quality conditions for crushed aggregate used in foundries are regulated by the SRPS B.B6.012 standard [19]. This aggregate serves as a flux additive in the production of grey, malleable, high-quality, and special cast iron.

Owing to their technological advancements, their favourable ecological characteristics, and the growing need for natural materials, carbonate mineral raw materials are gaining increasing importance, and their application and economic significance are increasing continuously. Today, these raw materials rank among the most important natural mineral resources. The broad application of carbonate raw materials in the economy is directly influenced by their physical, technical, and chemical properties [20,21,22].

The aim of this work was to conduct a mineralogical and chemical characterization of the stone from Jošanica quarry and, based on the results, propose its potential applications.

2. Materials and Methods

Sampling of stone predominantly comprising limestone was carried out at Jošanica quarry at three points: Jošanica Field 1, Jošanica Field 2, and Jošanica Field 3. At each sampling point, several samples were taken for chemical analysis; these samples were combined into one sample for mineralogical analysis. Using the quartering method, one sample was prepared from each field, resulting in three characteristic stone samples for mineralogical analysis of Jošanica quarry.

The stone samples (Jošanica quarry, Zvornik, Bosnia and Herzegovina) were prepared under laboratory conditions by grinding them to a particle size below 200 μm. A 100 g sample was taken for chemical analysis from the ground sample by using the quartering method.

2.1. Chemical Analysis of Stone

Calcium oxide content was determined complexometrically via titration with a standard solution of EDTA (complexone III) (Carlo Erba, Emmendingen, Germany), c(EDTA) = 0.02 mol/dm³), using murexide (Carlo Erba, Emmendingen, Germany) as an indicator. The endpoint of titration was indicated by the colour of the indicator changing from light pink to purple.

Total calcium oxide and magnesium oxide proportions were determined complexometrically using EDTA (c(EDTA) = 0.02 mol/dm³), with eriochrome black-T (Lach:ner, Prague, Czech Republic) as the indicator, with the colour changing from red to light blue. The content of magnesium oxide was calculated by subtracting the calcium oxide content obtained using the previous method from the total calcium and magnesium oxide content.

Loss on ignition was determined in a platinum crucible by heating the sample at 1000 °C until a constant mass was achieved.

Silicon dioxide content was determined gravimetrically by dissolving an aliquot of the sample with hydrofluoric acid (Lach:ner, Prague, Czech Republic) and precipitating it from the solution. The precipitate was filtered, washed, and calcined at 1100 °C, after which it was treated with hydrofluoric acid.

Chemical analysis of Na₂O, Al₂O₃, K₂O, Fe₂O₃, CuO, ZnO, Ga₂O₃, PbO, Cr₂O₃, TiO₂, and Ag₂O was performed using the X-ray fluorescence (XRF) method with an energy-dispersive X-ray fluorescence spectrometer—EDX-8000 (Shimadzu Corporation, Kyoto, Japan), which offers high sensitivity, resolution, and throughput for a wide range of applications, from general screening analysis to advanced materials research.

When a sample is irradiated with X-rays from an X-ray tube, atoms in the sample emit characteristic fluorescent X-rays. These X-rays have unique wavelengths and energies, characteristic of each element in the sample. Accordingly, qualitative analysis can be performed by examining the wavelengths of the emitted X-rays. Since the intensity of fluorescent X-ray radiation is a function of concentration, quantitative analysis can also be performed by measuring the intensity of X-rays at specific wavelengths for each element.

2.2. Mineralogical Analysis of Stone

X-ray diffraction (XRD) is a non-destructive experimental method based on X-ray diffraction. This method is used to identify minerals and determine the mineralogical composition of a material, as the type of mineral influences the final product’s properties and potential applications.

X-ray powder diffraction (XRPD) is used for the analysis and characterization of polycrystalline materials. It provides information about the phase composition, phase abundance, structure, and microstrain of a material.

XRPD can be used to analyse powdered samples, solid materials, and thin films with nanometer- to micrometer-sized grains, making it widely applicable for analysing various materials, including minerals, rocks, metals, alloys, ceramics, polymers, carbon-based materials, and composites. The key advantage of this method is its high precision and non-destructive nature, allowing a sample to be preserved for further analysis. Only 2 to 20 mg of material is required for analysis.

Diffraction measurements were performed using a Bruker D8 Endeavor powder diffractometer, operating on the Bragg–Brentano geometry principle, with a Ni-filter and an X-ray tube with a cobalt anode (CoKα radiation, λ = 1.78897 Å). The tube voltage was 35 kV, and the current was 40 mA. A scintillation detector was used to record the diffracted X-rays. Measurements were conducted over a 2θ diffraction angle range of 2° to 90°, with a 0.02° step size and an exposure time of 0.50 s per step.

Diffrac.EVA v 4.2.2 software was used to process the spectral data. The diffraction maxima positions (2θ in degrees), interplanar spacings (d in Å), and corresponding intensities (I) were tabulated. Based on the d-spacing values, and by comparing them with literature data and database searches, the crystalline phases present in the sample were identified.

3. Results and Discussion

Based on the chemical analysis of stone samples from the Jošanica area, it was concluded that the samples were predominantly composed of calcium, in the form of CaO, which indicates the presence of calcium carbonate in the stone samples. In samples 1a, 1b, and 1c from Field A, there was a significant presence of magnesium was detected in the form of MgO, which indicates the presence of magnesium carbonate, and dolomite. A significant amount of aluminium, present as Al₂O₃ (2–5%), and silicon, in the form of SiO₂ (0.5–6.0%), was present in the samples. The reduction in the values of the parameters following annealing at 1000 °C also shows that the presence of carbonates was significant (40–47%). Iron, as Fe₂O₃, was present in the range of 0.1–1.1%. Other components, given in

Table 1. Chemical analyses of stone from Jošanica quarry.

Component	Sample 1a-Field A	Sample 1b-Field A	Sample 1c-Field A	Sample 2-Field B	Sample 3a-Field C	Sample 3b-Field C
CaO, %	36.11	40.20	34.42	50.07	52.32	50.18
Na2O, %	0.270	0.210	0.782	0.356	0.02	0.110
MgO, %	12.52	10.05	13.53	0.96	0.47	0.32
Al2O3, %	2.50	3.13	2.79	4.75	2.02	4.98
SiO2, %	5.92	2.95	0.95	2.02	2.18	0.43
K2O, %	0.070	0.017	0.015	0.025	0.110	0.014
Fe2O3, %	0.920	1.050	0.504	0.639	0.640	0.189
CuO, %	0.010	0.010	0.012	0.011	0.012	0.045
ZnO, %	0.008	0.007	0.011	0.003	0.06	0.012
Ga2O3, %	n.d.	n.d.	n.d.	0.001	0.002	0.006
PbO, %	0.007	0.006	0.005	0.008	0.06	0.035
Cr2O3, %	0.019	0.016	0.015	0.013	0.009	0.014
TiO2, %	0.090	0.130	0.012	0.042	0.06	0.045
Ag2O, %	0.022	0.021	0.008	0.019	0.018	0.006
* LOI, %	41.57	42.20	46.58	40.90	42.08	43.52
Total, %	100.01	100.00	99.05	99.82	100.01	99.59

* LOI—loss on ignition.

, were present in insignificant amounts and did not significantly affect the quality of the stone.

Based on the chemical analysis of the content of CaO and MgO, the content of calcium carbonate (CaCO₃) and magnesium carbonate (MgCO₃) was calculated. The content of magnesium carbonate (MgCO₃), which was obtained via calculation based on the content of MgO, was used to determine the content of dolomite in the samples. According to the content of dolomite, the content of calcium carbonate, which is present in dolomite in its bound form, was calculated. Considering that the total content of CaCO₃ was higher than the content present in dolomite, it can be concluded that calcium carbonate is also present in some other form (

Table 2. Mineralogical characterization of stone from Jošanica quarry.

Component	Sample 1a-Field A	Sample 1b-Field A	Sample 1c-Field A	Sample 2-Field B	Sample 3a-Field C	Sample 3b-Field C
CaO, %	36.11	40.2	34.42	50.07	52.32	50.18
MgO, %	12.52	10.05	13.53	0.96	0.47	0.32
CaCO3, %	64.43	71.73	61.42	89.34	93.36	89.54
MgCO3, %	25.19	21.02	28.30	2.01	3.85	0.67
CaCO3·MgCO3, %	57.25	45.96	61.87	4.39	8.42	1.46
CaCO3,bound, %	31.10	24.96	33.60	2.38	4.57	0.79
CaCO3,free, %	33.33	46.77	27.82	86.96	88.79	88.75

). The data in Table 2 were obtained using the following formulas:

$$G_{Mg{CO}_3}={\displaystyle \frac{M_{MgC{O}_3}·\%MgO}{M_{MgO}}},\%$$

(1)

$$G_{dolomite}={\displaystyle \frac{M_{dolomite}·G_{MgC{O}_3}}{M_{MgC{O}_3}}},\%$$

(2)

$$G_{Ca{CO}_{3,total}}={\displaystyle \frac{M_{CaC{O}_3}·\%CaO}{M_{CaO}}},\%$$

(3)

$$G_{CaC{O}_{3,bound}}={\displaystyle \frac{G_{dolomite}·M_{CaC{O}_3}}{M_{dolomite}}},\%$$

(4)

$$G_{{CaCO}_{3,free}}=G_{Ca{CO}_{3,total}}-G_{CaC{O}_{3,bound}},\%$$

(5)

where

• $G_{Mg{CO}_3}$, $G_{dolomite}$, and $G_{CaC{O}_3}$ denote the content of magnesium carbonate, dolomite, and calcium carbonate (%);
• $G_{CaC{O}_{3,bound}}$ denotes the content of calcium carbonate in its bound form (dolomite) (%);
• $G_{{CaCO}_{3,free}}$ denotes the content of calcium carbonate in its free form (calcite) and in the form of other minerals (%).

According to the classification based on the literature, the stone samples we obtained from Jošanica quarry are considered to be of the limestone type because the presence of the mineral calcite is predominant in the samples. Based on the table, it can be concluded that samples 1a-field A, 1b-field A, and 1c-field A have a significant content of magnesium carbonate, according to which a significant presence of dolomite was determined, and such samples can be said to constitute limestone–dolomite. In samples 2-field B, 3a-field C, and 3b-field C, there is a slight presence of magnesium carbonate and a significant presence of calcium carbonate. These samples can be said to be exclusively of the limestone type (Table 2).

Mineralogical analysis of the stone samples confirmed the results of the chemical analysis. Based on the diffractogram of Sample 1-field A (Figure 1), dolomite was dominant in the samples, while the presence of calcite was also noted. This was confirmed by the chemical analysis of 1a, 1b, and 1c from field A. The presence of quartz at the 2θ 31 angle was also identified in the sample, and the chemical analysis also shows a significant presence of SiO₂ (1–6%). In the same sample, an insignificant amount of magnesium artinite, Mg_0.5H₄MgO₄, was identified (Figure 1, Table 1).

The mineralogical analysis of Sample 2-field B shows that calcite is predominant in the sample, and the minor presence of dolomite, quartz, and chlorite is also noted. Aluminium, in the form of zeosites, and iron, in the form of kronstedites, were also observed in traces, as confirmed by chemical analysis (Figure 2, Table 2).

The diffractogram of Sample 3, which was made as an intermediate sample of samples 3a and 3b-field C, shows that the dominant phase is calcite, and a minor presence of dolomite and coesite is also noted. In the sample, quartz was also registered at the 2θ 31 angle, as shown by the chemical analysis of the samples expressed as SiO₂ (0.5–2%) (Figure 3, Table 1).

Based on the results of the chemical analysis and the standard for the use of limestone in the paint and varnish industry (SRPS B.B6.032 [23]), Sample 3a-field C meets the requirements of the standard—which states that the loss on ignition and CaO content must range from 42.0 to 44.5% and 52.0 to 55.5%, respectively—and can be used in this industry. The samples 3a-field C and 3b-field C, based on the standards SRPS B.B6.012 for aggregate in foundries, SRPS B.B6.011 for aggregate in metallurgy, and SRPS B.B8.070 for mineral fertilisers, can be used in the cited industries [18,19,24]. According to these standards, the content of CaO_min = 50%, MgO_max content = 3%, SiO_2,max content = 2%, Al₂O_3,max content = 3%, and the maximum content of impurities is 6%. Moreover, samples 2 from field B and 3a and 3b from field C can be used for animal feed in accordance with the Official Gazette of the RS 31/98, 6/81, 2/90, 20/00, and 38/2001 [25].

According to the SRPS B.B6.032 standard, the same samples can be used in the paint and varnish industry for hydrocarbon mixtures and fillers for asphalt, for the neutralization of acidic soils, for mineral fertilisers, for the desulfurization of SO₂ gas in thermal power plants and heating plants, and for the production of PVC and in the plastics and carpet industry for the production of abrasives, adhesives, machine mortars, etc.

4. Conclusions

Based on the chemical analysis of samples 1a, 1b, and 1c, Field A is dominated by calcium, which is present as CaO. In these samples, the presence of magnesium, in the form of MgO, is significant. In 2-field B, 3a-field C, and 3b-field C, according to chemical analysis, calcium, in the form of CaO, dominates. In these samples, the presence of magnesium is insignificant. According to the results of our chemical analysis, based on calcium oxide, we calculated the total calcium carbonate content in all the stone samples, as well as for the fraction bound in the form of dolomite based on the presence of magnesium carbonate. In samples 1a, 1b, and 1c-field A, there was a significant presence of dolomite (57.25%, 45.96%, and 61.87%). The presence of calcium carbonate bound with dolomite was also significant (31.10%, 24.96%, and 33.60%), while the remaining calcium carbonate was present in the form of calcite or another form (33.33%, 46.77%, and 27.82%). Aluminium was present in all the samples, occurring as Al₂O₃, in the range of 2.00–5.00%. Silicon was also present, available as SiO₂, in the range of 2.00–6.00%. Iron was slightly rarer in these samples and ranged from 0.1–1% Fe₂O₃. Other trace impurities were present in insignificant amounts and did not significantly impact the quality of the stone. Our mineralogical analysis confirmed that in samples 1a, 1b, and 1c-field A, dolomite was the dominant phase, with a significant presence of calcite. According to this classification, this stone belongs to the limestone–dolomite group. In samples 2-field B, 3a-field C, and 3b-field C, calcite dominates, according to the mineralogical analysis, so the samples correspond to a limestone-type stone. In sample 3a-field C, impurities in the form of SiO₂, Al₂O₃, Fe₂O₃, and alkali were present at less than 6%. Therefore, the limestone from this locality can be used for the production of paints and varnishes. According to the corresponding standard, the required CaCO₃ content is 52.0–55.5%, and the loss on ignition should be 42.0–44.5%. This sample is also applicable in the cement industry due to its high CaO content, low MgO content (below the 4% limit for limestone in the cement industry), and very low alkali (sodium and potassium) content. Samples 3a-field C and 3b-field C can be used in metallurgy, as an aggregate in foundries, and for mineral fertilisers, as they meet the standard requirements for these applications. According to these standards, the required minimum CaO content is 50%, the maximum MgO content is 3%, the maximum SiO₂ content is 2%, the maximum Al₂O₃ content is 3%, and the content of total impurities should not exceed 6%. According to the SRPS B.B6.032 standard, these samples can be used in the paint and varnish industry, for hydrocarbon mixtures, as fillers for asphalt, for the neutralization of acidic soils, in mineral fertilisers, and for SO₂ gas desulphurisation in thermal power plants and heating plants.