# Characterization of Talcose Rocks Derived from
## 5 Discussion  
Talcose rocks (or talcocites/soapstone) consist largely of talc. They have a soapy feel and are soft enough to be carved with a knife [13]. They are very dense, non-porous rocks, in contrast with their serpentinite precursor. Testing on different soapstones around the world [14; 15] provides data that are compatible with the requirements of ASTM C97 for water absorption (0.1%, much lower than the one obtained for the Galicia local serpentinite (\(\approx\)0.70%, [2]). The compressive and flexural strength of some soapstone has shown values of 21 and 14 MPa. The former mechanical value is too low to accomplish the ASTM standards [14] to be used as dimension stone, but the flexural strength is quite high [15; 16]. We were not able to test our samples for the physical and mechanical behavior, as they were so fragile, but we intend to increase the sampling and implement other testing in future works. Talc has been used in pharmaceuticals for a long time as part of traditional Chinese medicine. Talcose rocks can be easily cut and carved, if necessary, for industrial applications, which should be further explored if other uses are not possible for these rocks. The analyses carried out on the samples from the two quarries in this pilot study, both mineralogical and geochemical, indicate a different composition, even though they come from rock outcrops mapped under the same nature (basic and ultrasonic rocks). This fact confirms the existence of significant variability within these rocks at almost the outcrop scale, contributing to reaffirming the geologic complexity of the Cabo Ortegal complex. The differences between both samples reside fundamentally in the talc content (more abundant in the Somozas sample) and in the presence of minerals from the serpentine group (more abundant in the Ferraria sample). The presence of both minerals could justify the discussion regarding the exploitation of these rocks for industrial use. Moreover, talc crystals, due to their relatively low cost and good heat resistance properties, as well as their hydrophobic characteristics, electrical insulation, lubrication, and acid resistance, are ideal as a surface for laboratory countertops and electrical switchboards. Figure 11: Trace elements in the study samples. Concentrations are in ppm. It is also an important filler, and it is widely used in many industrial fields, such as ceramics, paper, cosmetics, paints, food, ceramics, polymers, rubber, and insecticides [17; 18; 19]. For these reasons, in recent years, continuing interest has been expressed regarding the study of the deposits and characteristics of talc. However, talc is subject to contamination from other surrounding materials (i.e., serpentinites), such as heavy metals or even asbestos [9; 20], which is known to be a carcinogenic material. For example, talc ore extracted in the state of New York is heavily contaminated from tremolite asbestos, which results in a high mortality rate among workers [21; 22; 23]. In this scenario, very recently, a multinational pharmaceutical company was forced to pay billions in a settlement to resolve claims involving asbestos in its talc products, although it was not clearly demonstrated [24]. In the interest of finding some industry related to the ultramafic complex of Cabo Ortegal, an attempt to characterize the talose rocks that outcrop among the serpentinites has been carried out. The high content of Cr, Ni, and other heavy metals (contents of Y, Zr, Nb, Th, and U are even higher than in the serpentinite) preclude its use in the pharmaceutical industry. Indeed, in agreement with [19], the common presence of these foreign ions (i.e., Cr, Ni, etc.) in talc may prevent the high performance of this mineral. Nonetheless, based on thermal data, the tremolite contaminating the talc in the Somozas sample is not asbestos tremolite, which is a hazardous component. This gives us some hope of continuing with further characterization studies, because there might be a way of removing the impurities.