Siegfried Siegesmund - Monument Future

There was some controversy about the origin of the rock applied. In the Uruguayan small geological community, it was believed it was a facies of Pan de Azúcar Pluton. This pluton, studied in detail by Oyhantçabal (2005), is a km-size syenitic, quartz-syenitic and granitic circular intrusion, historically exploited with ornamental purpose (Morales Demarco, 2012). All efforts to localize the variety supposdly applied in Palacio Salvo in the area of the pluton were unsuccessful.

At the beginning of this study, 15 blueprints of the entire granitic façade were found by FADU in the General Archive of the Nation (Archivo General de la Nación). These blueprints have the localization and dimensions of around 1,000 pieces of the granitic façade of Palacio Salvo (the external façade and the façade of the passage, not studied in the present work), and some inscriptions written in German: Kösseine Granit Poliert , Grasyma Wunsiedel , Januar 1925 .

The ICG team compare the dimensions of the pieces applied in Palacio Salvo, with those stated in the blueprints. The match is perfectly accurate. Simultaneously, a communication with the German company allowed the confirmation as the providers of the rock and the undoubtedly identification as Kösseine Granite (Figure 1).

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.

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.

Table 3: Mechanical properties of Kösseine Granite.

No physical or mechanical tests were performed, nevertheless, results of Strohmeyer (2003) and Grimm (2018) were considered (Tables 2and 3).

Kösseine Granite shows a very good behavior against atmospheric agents, directly related to its physical properties: very low porosity, low water absorption, low water uptake coefficient and permeability. These properties show that the rock is practically impermeable, and consequently extremely stable to weathering conditions.

Mechanical properties for Kösseine Granite are typical of granitic rocks, even slightly higher. Comparing its UCS (uniaxial compressive strength) values to those of the statistical study of Mosch (2008), it can be observed that they are above the median. Flexural strength is also above the median of Mosch (2008), but the indirect tension is slightly below this parameter.

Abrasion resistance values are slightly higher than those reported by Morales Demarco (2012) for Uruguayan granitic rocks, but in the range of values given by Siegesmund & Snethlage (2011).

Figure 2:Ground floor plan (modified from FADU, 2019).

Figure 3:a. Perforation with metallic insert, oxide staining and star crack; b. Missing gap presumably a product of bursting or removal of metallic insert.