## 4 Discussion  
As was stated previously, drawing on the statements presented in [1] and basing on the results in Table 2, the original kurkar sandstone could be considered as a strongly anisotropic material. Generally, anisotropy is defined as a directional dependency of stone properties that determines the quality and resistance of stone against decay caused by harmful agents, such as water, salts, and air pollution [2; 3; 25]. Furthermore, kurkar sandstone's heterogeneous mineralogical composition hints at the possible deterioration when the stone is exposed to a hazardous environment. Micritic calcite (see Figure 11) has a poorly washed sandstone texture with a clay-enriched matrix that has not been leached yet [16; 17]. Calcite, CaCO\({}_{3}\), is one of two main minerals of kurkar sandstone. Weathering of calcite in the offshore zone might dissolve its calcium ions and form gypsum crust at the stone surface. The breeze shoves salty seawater into the stone. This salted water is intensively absorbed by porous kurkar because of capillary forces. Therefore, the pore solution becomes gradually supersaturated. Thus, the salts like halite, NaCl, sanderite, MgSO\({}_{4}\cdot\)2H\({}_{2}\)O, epsomite, MgSO\({}_{4}\cdot\)7H\({}_{2}\)O, thenardite, Na\({}_{2}\)SO\({}_{4}\), mirabilite, Na\({}_{2}\)SO\({}_{4}\cdot\)10H\({}_{2}\)O and gypsum, CaSO\({}_{4}\cdot\)2H\({}_{2}\)O might crystalize from the supersaturated pore solutions. Their crystallization is followed by the very high crystallization pressure (\(\sim\)100 MPa) destroying stone [28]. Accelerated weathering test of kurkar stone in sodium sulfate solution, see Figure 13, has shown that kurkar sandstone is prone to destructive pressure during salt crystallization. The physical and mechanical properties of kurkar sandstone have been worsened after natural weathering in the Panorama Sea Wall, see Table 2, and after the accelerated weathering test, as well. Both weathering processes, the environmental one and the accelerated one, have caused a loss of stone material and led to the efflorescence process. The tests carried out in the current study have reaffirmed the standard accelerated-weathering test [27] in predicting stone durability's trends. Thus, an accelerated weathering test before setting the stone in outside veneers might help ensure their quality. Unfortunately, this test was disregarded entirely during the construction of the Panorama Sea Walls. The petrographic analysis, Figure 12, has revealed the substantial amounts of feldspar minerals in kurkar sandstone. XRD analyses have explained that the type of feldspar in kurkar sandstone is albite. Biotite (sodium aluminum silicate) found in kurkar sandstone is a phyllosilicate mineral in the common mica group. Unfortunately, the years 1995-2015 were characterized by extremely high levels of air pollution (NO\({}_{\text{x}}\), SO\({}_{2}\), and CO\({}_{2}\)) in Haifa and Acre Bays adjacent to the big industrial zone and the high traffic areas (The historical data on the levels of air pollution could be found in the database of Israeli Ministry of Environmental Protection ([[https://www.gov.il/en/departments/topics/reducing_air_pollution](https://www.gov.il/en/departments/topics/reducing_air_pollution)]([https://www.gov.il/en/departments/topics/reducing_air_pollution](https://www.gov.il/en/departments/topics/reducing_air_pollution))). Following a 2015 government decision, implementing the 2015-2020 National Plan to Reduce Air Pollution in Haifa and Acre Bays began in 2016. The National Plan, which has a budget of NIS 115.5 million, is expected to reduce industrial air pollution in the Haifa Bay vicinity, incl. Acre Bay by 50% [29; 30; 31]. According to the NUMBEO database, the air pollution index in Acre, Israel is ca. 75, which is high [31]). Weathering of albite feldspar and biotite mica under these conditions might cause their chemical alteration and decomposition under the following scenario:1.