To log the cache answer and fulfill the following tasks:

1. Have a closer look at the High Cross, describe the sandstone texture in your own words.  
2. Observe the sandstone and estimate the percentage in which the sandstone consists of the sand grains. Which percentage of the sandstone is the matrix?
3. Based on your observation which weathering processes mentioned below in the listing can be directly observed in the sandstone?
4. Based on your assumptions and observations which weathering processing which are not necessarily observable could be causing the weathering of the sandstone High Cross?  
5. As proof of your visit attach a photo of an object belonging to you with the High Cross in the background

Source: National Library of Ireland.

Drumcliffe

Drumcliffe is special for many reasons. It is a resting place of one of the most important literary figures of Irish and European literature, W.B. Yeats. Right by the grave we can admire architecturally beautiful church. Drumcliffe is also an important historic site where already in 6th century Christian monastery was built. As we arrive by car or bus we can see remains of a 11th century tower right by the road. By the carpark, on the other hand, we can appreciate what is to be considered, one of the most interesting, unique and beautiful High Crosses in Ireland.  

William Wakeman's watercolour of the high cross and round tower at Drumcliffe, around 1880. County Sligo Library. 

Drumcliffe High Cross

The highly decorated Drumcliffe High Cross is made of sandstone and may date from the 11th century. This High Cross is about 4 meters high. On both the east and west side it features animals. On the west face the subjects include the Presentation in the Temple and the Crucifixion. The east face bears Adam and Eve, Cain and Abel, Daniel in the Lions’ cave and a Lion in high relief. It has been used as a mean to tell bible stories to the passers-by. In monasteries books have been written. However, through the depiction on the cross the stories of the Bible were made available also to those who were not able to read or did not have access to the books.   

Own photo

As we admire the cross, we see however, that it is has been slowly losing its intricate details and without the help of description it is difficult to decipher the stories and figures depicted on the Drumcliffe High Cross. The cross is made out of sedimentary rock, sandstone. Unfortunately it is prone to weathering. We can say with high certainty that the details carved in the stone were much more clearly visible to observers 1000 years ago.   

Sandstone

Sandstone, which is the material used for carving the cross is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. They form the primary architectural element of a sandstone. The silicate minerals (quartz or feldspar) of which the sand grains are composed of are the most resistant minerals to weathering processes at the Earth's surface. That is the reason that uncemented sand is so common on the surface of our planet. However, the weathering resistant silica minerals are only one component of the sandstone rock. The spaces between the sand grains in a sandstone rock are filled, to varying degrees by much finer sediment – or matrix. As opposed to sand grains the matrix is highly reactive in both mechanical and chemical contexts. This fact defines the property which determines if the particular sandstone is less or more resistant to weathering.

Common sandstone weathering processes

Ice crystallization, also known as ‘ice wedging’ or ‘frost wedging’, is a process that occurs when water is allowed to seep into a pore or crack in the sandstone where it freezes (as water expands when frozen, this could fracture the stone).

Salt crystallization is a process that occurs when a saline solution is permitted to enter the pores or cracks of your sandstone, where it crystallizes and expands. This can either widen existing cracks or even cause the stone to fracture.

Expansion and contraction are naturally occurring cycles that cause your sandstone to weaken over time. It occurs as the stone is heated and cooled or is wetted and dried.  

Lichens and other growths can also damage your sandstone, as they produce chemicals that break down the stone. It can also cause more cracks and holes to appear.

Wind can also carry fine particles which are very abrasive and can cause serious erosion to sedimentary rocks such as sandstone.

Sources:
http://www.megalithicireland.com/High%20Cross%20Drumcliffe.htm
http://www.carrowkeel.com/sites/crosses/drumcliffe.html
https://www.askaboutireland.ie/reading-room/environment-geography/physical-landscape/the-wakeman-drawings/drumcliff/high-cross/
https://www.geological-digressions.com/the-mineralogy-of-sandstones-matrix-and-cement/
https://www.yarrabeestone.com.au/blog/understanding-the-effects-of-weathering-on-sandstone