Rock quality is an important consideration in geological and engineering activities. The ability of a rock to withstand pressure, deform under stress, and maintain its structural properties can influence how the material is assessed for engineering purposes. Previous geological conditions can also alter mineral composition, potentially changing the mechanical behavior of rocks.
The research focused on the Loli Saluran area in Donggala District, Central Sulawesi Province, an area located within the Tinombo Formation and characterized by volcanic and intrusive rocks. The researchers examined how differences in mineral composition were associated with variations in rock strength and other mechanical characteristics.
Three Rock Samples Represented Eleven Observation Points
The research team collected observations from 11 data collection points in the study area. Three rock samples were selected to represent the main geological characteristics found at those locations: one diorite sample from Station 02 and two porphyritic meta-andesite samples from Stations 06 and 09.
The researchers examined the samples using several laboratory and geological methods. Rock specimens were tested under increasing pressure until failure to measure their uniaxial compressive strength, as well as Young’s modulus and Poisson’s ratio.
The mineral composition of the same samples was then examined using X-Ray Diffraction (XRD), which identified the percentage of minerals contained in each rock. Petrographic analysis using thin rock sections and a polarizing microscope was also used to identify and validate the rock types and visible mineral characteristics.
The research team then compared mineral composition with mechanical test results through regression and correlation analysis. This approach allowed the researchers to measure how closely changes in mineral percentages were associated with changes in rock mechanical properties.
Plagioclase Was Linked to Stronger Mechanical Properties
The study identified plagioclase, quartz, and chlorite as the three minerals that could be consistently compared across the tested samples.
The diorite sample from Station 02 contained 51.6 percent plagioclase, 33.1 percent quartz, and 15.3 percent chlorite. The porphyritic meta-andesite sample from Station 06 contained 59.7 percent plagioclase, 29.7 percent quartz, and 8.4 percent chlorite, while Station 09 contained 56.1 percent plagioclase, 31.9 percent quartz, and 8.2 percent chamosite, a mineral included in the study’s mineral comparison data.
Mechanical testing produced different results for each sample. Station 02 recorded a compressive strength of 4.02 MPa, Station 06 reached 24.33 MPa, and Station 09 recorded 13.48 MPa. Among the three tested samples, Station 06 had the highest measured compressive strength.
The strongest positive relationship was found for plagioclase. According to the authors, plagioclase showed correlation coefficients ranging from 0.994 to 0.997 with compressive strength, Young’s modulus, and Poisson’s ratio. These results were categorized in the study as very strong relationships.
The researchers reported that higher percentages of plagioclase were associated with higher mechanical property values in the tested rocks. The reported coefficients of determination ranged from approximately 98.35 percent to 99.45 percent for the relationships discussed in the study.
Quartz and Chlorite Showed Negative Relationships
Quartz showed the opposite pattern. The study found a very strong negative relationship between quartz content and the mechanical properties measured in the rock samples.
The reported correlation coefficients for quartz ranged from -0.944 to -0.992. According to the researchers, lower quartz percentages in the tested samples were associated with higher values of compressive strength, Young’s modulus, and Poisson’s ratio.
The authors noted that quartz is generally known as a resistant mineral, but its effect on rock strength can depend on the texture and internal structure of the rock. In the tested samples, quartz occurred as phenocrysts that may create gaps between minerals, potentially reducing compressive strength.
Chlorite also demonstrated a negative relationship with rock mechanical properties. Correlation coefficients ranged from -0.832 to -0.928, indicating a very strong relationship according to the classification used by the researchers. Higher chlorite content was associated with lower compressive strength, Young’s modulus, and Poisson’s ratio.
“The higher percentage of plagioclase determines the higher value of mechanical properties, while higher percentages of quartz and chlorite determine lower mechanical properties,” the findings of Muslimin U. Botjing, Bey Nida’ul Hasanah, and Nunik Rezkiarti Janat of Tadulako University indicate.
Potential Implications for Geological and Engineering Assessment
The findings suggest that mineral composition can provide useful information when evaluating the mechanical characteristics of rocks. In the Loli Saluran samples, higher plagioclase content was associated with stronger mechanical properties, while quartz and chlorite showed negative relationships with the measured parameters.
This information may be relevant to geological investigations and engineering assessments where understanding rock quality is necessary. However, the authors emphasized that mineral composition is not the only factor influencing rock strength.
They recommended future studies using a larger number of samples and rocks dominated by specific minerals to better isolate the influence of each mineral. Future research should also examine other factors, including rock density, porosity, weathering conditions, and discontinuities, because these characteristics may also affect mechanical behavior.
Author Profiles
Muslimin U. Botjing is the corresponding author of the study and is affiliated with the Geological Engineering Study Program, Civil Engineering Department, Faculty of Engineering, Tadulako University. The article does not provide a complete academic degree or detailed biographical profile beyond the institutional affiliation and research contribution.
Bey Nida’ul Hasanah is a co-author affiliated with the Geological Engineering Study Program, Civil Engineering Department, Faculty of Engineering, Tadulako University. The published article does not specify the author’s academic degree or detailed field-of-expertise profile.
Nunik Rezkiarti Janat is also a co-author from the Geological Engineering Study Program, Civil Engineering Department, Faculty of Engineering, Tadulako University. Specific academic degrees and detailed professional specialization are not provided in the source article.
Source
Article Title: The Relationship of Mineral Composition to the Mechanical Properties of Rocks in Loli Saluran Area Donggala District Central Sulawesi Province
Authors: Muslimin U. Botjing, Bey Nida’ul Hasanah, and Nunik Rezkiarti Janat
Journal: Formosa Journal of Science and Technology (FJST)
Publication Year: 2026
Volume and Issue: Vol. 5, No. 8
Pages: 2077–2096
DOI: https://doi.org/10.55927/fjst.v5i8.125
Official Journal URL: https://journalfjst.my.id/index.php/fjst
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