## 5 Discussion
Nonetheless, fertile mantle sources may be subjected to extensive degrees of partial melting, especially within SSZ settings [50; 51; 81; 85], leading to lithologies enriched in orthopyroxene, spinel and olivine such as harzburgite, massive dunite and dunite-chromitite assemblages. Therefore, the F.R. can provide constraints regarding the geological settings of formation, whether or not these were affected by slab-related or rift-associated processes, but also the preservation degree of primary mineral phases. As can be seen in Table S4, the values of the F.R. of the examined ultramafic rocks range from 0.024 to 0.567 showing a wide range of fertility, which has an immediate effect on the mineralogy and geochemistry of each sample. It is thus expected that less fertile rocks have been subjected in higher partial melting degrees leading to lithotypes deprived of clinopyroxene grains. Apart from the fertility, another important factor that may significantly modify the nature and characteristics of the ultramafic rocks is serpentinization (as it constitutes the basic alteration of the ultramafic rocks) and may take place in a wide variety of environments: the mantle wedge, ocean floor and exhumation-related environments, with the latter tending to be more prominent [33; 34; 86; 87]. During this process, mainly olivine but to a certain extent orthopyroxene can be replaced predominantly by serpentine, which leads to the removal of mobile trace elements and the formation of depleted and serpentinized ultramafic rocks [88; 89]. Serpentinization is often facilitated by discontinuities within rock formations such as faults, shear zones leading to distinctive cataclastic textures; however, it has also been proven that the reactions during serpentinization can assist rock fracturing [90; 91; 92]. Alteration processes can be quantified using the measured L.O.I. contents. Loss of ignition (LOI) represents a chemical expression of the alteration degree of rocks; the main type of alteration is serpentinization in the present studied rocks, hence it is adequately translated into their degree of serpentinization [16; 26]. The F.R. relies highly upon the clinopyroxene modal composition and thus, in order to quantify the effects of serpentinization relative to olivine modal composition, we introduce the following Equation (2) that determines the Ultramafic Rock Health Index (U.R.H.I.) (Table S4):  
\[\text{U.R.H.I.}=\text{F.R.}+\text{modal olivine}(\%)/100-\text{L.O.I.}/100 \tag{2}\]  
This index aims to assess and quantify the overall health conditions, encompassing the two major modifying factors that include removal of primary mineral phases, as well as the extent of serpentinization. A non-altered and highly fertile ultramafic rock of Iberzolite composition, representing Primitive Mantle composition, would obtain an F.R. value of \"1\", modal olivine 55% and L.O.I. value of \"0\", due to the absence of serpentinization. Thus, the Normalized U.R.H.I. (U.R.H.I.N) can be obtained through by dividing the U.R.C.I. by 1.55, as described through Equation (3) (Table S4):  
\[\text{U.R.H.I.}_{\text{N}}=\text{U.R.H.I.}/1.55 \tag{3}\]  
The applicability of the U.R.C.I.N was examined in relation to the mechanical properties of the ultramafic rocks of our study suite, namely: moisture content (w in %), uniaxial compressive strength (UCS (MPa)), Los Angeles abrasion value (LA (%)) total porosity (n\({}_{\text{t}}\) (%)), soundness test (S (%)), point load strength (I\({}_{\text{s(50)}}\) (MPa)). Although most of the above tests are multifactorial (depending on mineral size, mineral geometry, texture), the decisive factor is the serpentinization, i.e., the ratios of primary minerals/serpentine. In all cases, except LA (%), two groups were noted, one consisting of slightly to moderate altered ultramafics (L.O.I. \(<\) 11.4) and the second consisting of the highly serpentinized lithologies (L.O.I. 13.4-15.3) (Table S2). Positive correlations are noted for the cases of UCS (MPa), LA (%) (Figure 7a,b) and I\({}_{\rm{(50)}}\) (MPa) (Figure 8a).