## 5 Discussion
), while samples from those born in a forearc environment are considered unsuitable for concrete aggregates as is shown in the diagrams of Figure 11.  
Figure 9: (a) Al\({}_{2}\)O\({}_{3}\)/SiO\({}_{2}\) vs. MgO/SiO\({}_{2}\) diagram of periodtites from the Veria–Naousa and Gerania ophiolite complexes (fields after: [94]); (b) Correlation diagram of Fluid Mobile Elements (FME: Pb, As, Sb, Th, U, Sr) versus the normalized Ultramafic Rock Health Index (U.R.H.I.N). The field of ultramafic hosted within a forearc mantle section (Veria–Naousa ophiolite) consists of samples with elevated FME concentrations coupled with low U.R.H.I.N, whereas the MOR field consists of samples with variable U.R.H.I.N and low FME concentrations (Gerania ophiolite). Figure 11: Diagrams of the suitability of ultramafic rock samples from the Veria–Naousa and Gerania ophiolite complexes for (**a**) the LA(%) test; (**b**) the UCS (MPa) test; (**c**) the S (%) test. Figure 10: Cr# vs. Mg# [Cr# = 100 \(\times\) Cr/(Cr + Al); Mg# = 100 \(\times\) Mg/(Mg + Fe\({}^{2+}\))] diagram of spinel-group minerals hosted within the Veria–Naousa and Gerania peridotites. Fields of boninite [95,96], forearc peridotite, backarc peridotite, and abyssal peridotite [97] are shown for comparison. This fact indicates for the first time in ultramafic rocks that the environment of their genesis is the determining factor for their physico-mechanical characteristics, while weathering phenomena seem to affect their properties in a lesser amount because of the similar age of the studied samples and of the similar prevailing weather; significant differences in these properties cannot be attributed to any other factor. It is obvious that the suitability of the studied rock samples is relevant to the impact of mineralogical and structural characteristics ultramafic ophiolite rocks from two different ophiolite complexes (Veria-Naousa and Gerania complexes). These rocks present different mineralogical composition and textural characteristics as a result of their different degrees of serpentinization which affects their suitability as aggregates. Lhezolite and harzburgite from the Veria-Naousa ophiolite complex display higher degrees of serpentinization (Table S1) in contrast to those from the Gerania ophiolite complex and of ol-orthopyroxenite (Table S1). Lhezolites and harzburgites from the Veria-Naousa ophiolite complex present mainly cataclastic and mesh textures in cases where serpentine is dominant in a percentage from 89.40 to 94.80% (Table S1) with few relics of primary minerals (clinopyroxene and orthopyroxene). More specifically, the intensively serpentinized peridotite exhibit mainly smooth surfaces due to their high content of serpentine, which creates a smooth micro-topography. On the other hand, the microroughness of the studied fresh to moderate serpentinized peridotite proved significantly high, as indicated by SEM images (Figure 6). This texture is attributed to the existence of both \"soft\" serpentine, which forms smooth surfaces, and \"hard\" olivine, orthopyroxene, clinopyroxene and spinel, which form rough projections. In these samples, it is noticeable that the uniform distribution of serpentine helps the renewal of the micro-roughness. All the factors mentioned above indicate the suitability or not of ultramafic rocks as concrete aggregates. All of the above on the one hand provide useful data to the entire international scientific community regarding the direct impact of the rocks' birth environment on their properties and their suitability for concrete applications. On the other hand, the findings contribute to energy saving and waste reduction, as well as through geochemistry of ultramafic rocks, demonstrating it is possible to predict the properties, the suitability and therefore the dynamics of an area for mining.