Sir John Gray sometimes spelled John Grey was an Irish physician, surgeon, newspaper proprietor, journalist and politician in the mid to late 1800s. Gray was active both in municipal and national government for much of his life, and had nationalist ideals – which he expressed as owner of the Freeman's Journal, chairman of the Dublin Corporation Water Works Committee between 1863 and 1875, and Member of Parliament in the House of Commons of the then United Kingdom of Great Britain and Ireland, for Kilkenny City from 1865 until his death. He was a supporter of Daniel O'Connell, and later of Charles Stewart Parnell, and advocated a repeal of the Act of Union. His greatest achievement however was through his offices with Dublin Corporation. The Vartry Reservoir water supply works were completed, introducing a fresh water supply to Dublin City and County. Shortly after his death, his contributions to the provision of the water supply, and the beneficial impact this had to conditions of public health in Dublin, were recognised in a memorial statue on O'Connell Street. This white statue and plinth is what you are now looking at.
But enough history, Geology time!!
Sir John Grays statue and plinth are made entirely out of Sicilian Marble quarried primarily in the Custonaci area of the Sicilian province of Trapani. This Sicilian marble, varieties of which can be found in important architectural works such as churches, cathedrals and palaces, features throughout entire periods in history. And here it is in Dublin, right under the noses of all the tourists you see around you.
Marble is a metamorphic rock, resulting unsurprisingly from metamorphism of sedimentary carbonate rocks, most commonly limestone or occasionally dolomite rock. The process is as follows: Often, sediment from dead plants and animals collects at the bottom of the sea, where it gets crushed by layers and layers of further sediment. The great pressure, sometimes combined with intense heat from say, a nearby volcano causes the rock to change chemically, or metamorphose. Metamorphism causes variable recrystallization of the original carbonate mineral grains. The resulting marble rock is typically composed of an interlocking mosaic of carbonate crystals. Primary sedimentary textures and structures of the original rock (known as protolith) have typically been modified or destroyed.
The degree of metamorphism of a rock is controlled by three main factors:
Heat. As a rock is continuously buried at depth it will be subjected to an increasing amount of heat from the inner earth (or a volcano). This heat can change the carbonate minerals structure.
Pressure. As the carbonate rock is continuously buried it is subjected to increased lithic pressure which will also alter the carbonate material.
Time. Depending on how long this carbonate material is buried for before subsequent uplift to the surface it will effect how long it is effected by heat and pressure.
Heres a diagram:
Pure white marble is the result of metamorphism of a very pure limestone or dolomite protolith. The characteristic swirls and veins of many colored marble varieties are usually due to various mineral impurities such as clay, silt, sand, iron oxides, or chert which were originally present as grains or layers in the limestone. Green coloration is often due to serpentine resulting from originally high magnesium limestone or dolostone with silica impurities. These various impurities have been mobilized and recrystallized by the intense pressure and heat of the metamorphism. Sicilian marble, such as that which you see in John Grays statue, appears to have very few impuraties.
Marble has been prized for its use in sculptures since classical times. This preference has to do with its softness, which made it easier to carve, relative isotropy and homogeneity, and a relative resistance to shattering. Also, the low index of refraction of calcite allows light to penetrate several millimeters into the stone before being scattered out, resulting in the characteristic waxy look which gives "life" to marble sculptures of any kind, which is why many sculptors preferred and still prefer marble for sculpting. With all your reading out of the way, it's now time to 'sculpt' your own answers.
Please answer the following questions via an email sent to my profile above. Ensure you send your email address and caching name, it makes life easier!
1) There are three general classifications of rock. What type is marble? What are the other two types?
2) Is marble considered a soft or a hard rock? Do you think it would shatter?
3) Measure the length and width of the stone shown here. Creative units are welcome.
Note: If you do not have the photo in the field, measure the large horizontal stone on the south side of the plinth, directly below the curved bit underneath "Died April 9 1875".
4) Look very very VERY closely at the marble of the plinth. What colour grains do you see? Can you see any evidence of the original protolith, or is it gone?
5) Run your fingers along the length of the plinth. Is the marble perfectly smooth, or are there small dips and peaks? Measure approximately the size of a dip/peak if you find one.
Go ahead and log this cache if you feel you have answered the questions correctly or made a decent attempt! I'll contact you if there are any problems. Due to volume on this earthcache, I can get behind on emails but you do not have to wait for my reply to log this!
Some Tourist Information:
Since this cache will hopefully be found by many visitors to Ireland, here are some local must-do caches. If you'd like to do a 'rare trio' of cache types involving this Earthcache, there is also a virtual on O'Connell street at the spire (GCE388, Stiffy by the Liffey) and a webcam a short walk away (GCJKTN, Gardiner's Treat). These are March '03 and June '04 respectively, so may be useful for Jasmer grids as well.
Also, incase you don't know, the first Geocache ever placed in Europe, (GC43, Europes First) is about 20km away in Bray. You can park at the co-ordinates in the listing, or walk to Connolly Station in Dublin, about 200m from here (N53° 21.095 W6° 14.991) and get a Southbound DART to Bray Daly. It is a 20-30 minute walk from there uphill and is a really lovely location for a historic cache, and almost certainly a Jasmer (June '00). Return by getting a Northbound DART to Dublin Connolly. Jasmer Tourists in the area may also be interested in the extremely rare month provided by GC322, Kyle Cache 1 (Feb '01), which is a short drive from Dublin but cannot be reached using public transport. There is no parking waypoint provided, but there is space for a car at N 53° 10.105 W 006° 09.836, provided you make sure all your valuables are hidden while you make the 40 minute round-trip.
Note: O'Connell Street is generally a safe place for tourists but nonetheless, I'd recommend doing this cache early in the morning. It is NOT a cache to be done late at night for safety and sanity reasons.
Note 2:**PLEASE NOTE. Luas Cross City works have erected a fence around the statue. I am aware Q4 and Q5 are difficult at the moment but try your best. I'll be fair and won't deprive you of an Earthcache find!!