# Mineralogical Transformations in Granitoids during Heating at Fire-Related Temperatures
## 3 Results  
### Petrographic Description  
Main features of the selected granitoids are shown in Table 1.  
Eagle Red (ER) is a medium-coarse grained reddish alkali-feldspar-rich granite quarried from the Wiborg batholite in the south of Finland. It is characterized by almost 50% reddish feldspar, which gives it its commercial denomination. Alkali feldspar is orthoclase or microcline in similar proportions and with pertittic transformation. Alkali feldspars showed mainly inter and intracrystalline fissures. The quartz proportion is approximately 30% and displays equidimensional habit. Quartz is remarkably fissured, with mainly intra and transcrystalline fissures, often filled with secondary minerals. Plagioclase comprises approximately 15% of the rock and has a euhedral habit and low weathering. Mica is mainly biotite and appears as small crystals accounting for less than 10% of the rock. Secondary and accessory minerals are muscovite, apatite, rutile, and chlorite (Figure 2).  
Grassal (G) is a coarse-grained grey Calc-alkaline post-kinematic monzonite from the northwest of Spain. Quartz and alkali feldspars account for approximately 30% of the rock each. Alkali feldspars are either orthoclase or microcline, some of them with pertititexture. Fissuration is mainly intracrystalline. Quartz is euhedral and of homogeneous size, with numerous fissures, mainly inter and intracrystalline. Plagioclase comprises almost 20% of the rock and it shows an advanced weathering degree in the nucleus and on the edges that are in contact with biotite. Biotite mica forms approximately 15% of the rock and it is deeply weathered (chloritization). It also exhibits numerous inclusions of zircon and opaque minerals. Secondary and accessory minerals are amphibole, chlorite, and sericite (Figure 2).  
Golden Ski (GS) is a fine-grained peraluminous syn-kinematic yellow monzogranite. GS is quarried in southern Pontevedra (Spain). The main difference with the rest of the studied granites is its mineral orientation, shown mainly by micas. This monzogranite has only 15% of alkali feldspar, which is mainly orthoclase. Orthoclase is euhedral to subhedral, with intracrystalline fissures and weathered centres. Quartz is the main mineral (more than 30% of the rock), widely fractured with inter, intra, and transcrystalline fissures. Plagioclase forms approximately 20% of the rock and it is severely weathered to sericite and highly fissured. Mica is relatively abundant with approximately 20% muscovite and 10% biotite. The former shows tabular habit although some edges exhibited corrosion signs, whereas the latter shows euhedral habit and no evidence of chloritization (Figure 2).  
Negro Galicia (NG) is a post-tectonic hypabyssal black tonalite assigned to \"Basic Dikes\" unit. NG is a homogeneous fine-grained stone (\(\approx\)3 mm) quarried in northern Pontevedra (northwestern Spain). The mineral composition is more complex with 30% of mica and the rest equally repartitioned between quartz, feldspar, and amphibole-pyroxene. Alkali feldspar is mainly orthoclase, with rough boundaries due to its advanced weathering degree. Quartz showed intracrystalline fissuration with sericite from feldspars alteration filling the cracks. Plagioclase was widely fissured and altered to sericite, mainly in the nucleus. Biotite appeared forming 25% of the stone and muscovite only 5%. The first one showed slight chloritization and the second one tabular habit. Amphiboles showed euhedral habit and well defined cleavage plans (Figure 2).