Environmental Engineering Reference
In-Depth Information
Figure 8.1.
Alabaster block at Knossos Palace, Crete. Dissolution features
are clearly visible on the top and lateral sides of the stone
Some minerals, although their resistance to water dissolution is high, create
significant problems if a stone happens to contain them. This is the case of swelling
clay minerals and pyrite (FeS
2
). This last mineral, present in a siliceous chalk called
Tuffeau in the Loire region in France, generates significant discoloration and stone
loss (see Figure 8.2) when it oxidizes and reacts with water, according to the
following chemical reaction [WIN 94]:
2FeS 7O 16H O 2FeSO .7H O 2H SO
+
+
→
+
2
2
2
4
2
2
4
FeSO .7H O
→+
FeSO
7H O
42
4
2
(
)
( )
12FeSO
+
3O
+
6H O
→
4Fe
SO
+
4Fe OH
4
2
2
2
4
3
3
(
)
( )
Fe
SO
6H O
+
→
2Fe OH
+
3H SO
2
4
2
2
4
3
3
Figure 8.2.
Stone loss and discoloration of a siliceous chalk
from the Loire region in France
