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Due to the impossibility of sampling the rock in the buidling, as it is a National Historical Monument, a preliminary petrographic characterization was performed in situ. It is a very coarsed-grained leucocratic rock, yellowish white, to beige and greyish light brown. This is not the typical color of Kösseine Granite, but a yellowish variety that is also widely used in Germany.

The rock shows a porphyritic texture, due to the presence of alkali feldspar up to 3.5 cm, most around 2 cm, subhedral, frequently rounded. Some show zoning with a light brown core, sometimes euhedral, surrounded by a greyish white mantle. Most are grey. Inclusions of biotite (Strohmeyer, 2003) are very frequent, often evidencing growth rims. Occasionally, a translucent mineral can be observed, that gives the rock a pearl luster, this is probably plagioclase.

Figure 1: Right: Brochure of Palacio Salvo in construction with promotional poster of Grasyma (courtesy of Claus Wölfel).

Quartz is interstitial between feldspar and biotite, with light brown to beige color. Biotite shows sometimes hexagonal sections with dark reddish to coppery color. Muscovite is silver grey sometimes with greenish hues. Both minerals frequently form nests, and the biotitic sometimes show orange oxidation rims.

Garnet is present as an accessory mineral in mm euhedral to subhedral red crystals with vitreous luster. They occur occassionally as inclusions in alkali felspars, sometimes in matrix minerals.

Table 1: Mineralogical composition of Kösseine Granite.

Mineral (%)	Grimm (2018)	Strohmeyer (2003)
Alkali feldspar	41	32
Quartz	36	26
Plagioclase	13	30
Biotite	6	10
Muscovite y chlorite	2	1
Accessory	2	< 1%

The rock structure is characterized by the presences of elongated mafic enclaves, up to 20 cm with aspect ratio up to 1 : 20, some banded (mafic and felsic bands). Small rounded mafic enclaves are also present (2–3 cm). Felsic enclaves up to 40 cm 109ocurr either as fine to very fine-grained or as very coarsed-grained. All these structural elements disrupt the rocks décor. The rock is classified according to its mineral composition (Table 1) as a granite (Strohmeyer, 2003; Grimm, 2018).

Table 2: Physical properties of Kösseine Granite.

Physical properties (units)	Grimm (2018)	Strohmeyer (2003)
Bulk density (g/cm3)	2.67	2.67
Matrix density (g/cm3)	2.69	2.68
Porosity (% vol)	0.71	0.11
Average pore radii (µm)		0.02
Volume of capillary pores (% vol)		0.02
Water absorption (wt%)
Water absorption (atm) (wt%)	0.21
Water absorption (vac) (wt%)	0.27
Saturation coefficient S	0.79
Water absorption coefficient [kg/m2*√t]		0.003
Permeability (mD)	0.002
Specific surface (m2/g)	0.22
Thermal expansion coefficient (10–6K–1)		9.22

Table 3: Mechanical properties of Kösseine Granite.

Mechanical properties (units)	Strohmeyer (2003)
x-direction	y-direction	z-direction	Average
UCS (MPa)	194 ± 11	194 ± 10	199 ± 8	195 ± 17
Indirect Tensile Strength (MPa)	12.2 ± 1.2	10.9 ± 1.3	12.5 ± 1.5	11.9 ± 2.3
Flexural Strength (MPa)	18.0 ± 1.1	19.7 ± 1.1	22.6 ± 0.8	20.1 ± 1.7
Abrasion Strength (cm3/50 cm2)	5.8 ± 0.2	5.7 ± 0.1	5.6 ± 0.1	5.7 ± 0.2