|While most visitors expect Rome to made of endless white marble there are a range of stone types from around the far reaches of the Roman Empire.|
|This stone was reserved for the most important monuments and people because of its color.|
|Many of the most famous breccias originated in Turkey. |
Some of the multicolored stones have a metamorphic origin. Rather than being separate pieces of stone that were stuck back together, this gneiss (pronounced nice) was a solid piece of rock that was put under great pressure and heat to deform it.
|In metamorphic rocks some of the elements moved from their previous crystals to form new crystals (like the big pink one) and give it a whole new texture.|
|Other stones have a complicated history. This one may have been a breccia that was later heated and squished (metamorphosed).|
|These crystals have dissolution textures on their edges which suggest that they were in contact with hot fluids (or melt) that were different than the one they formed in.|
|There were also many pieces made out of agate. Agate forms by the growth of minerals (silica) inside some sort of crack or void in a volcanic rock. |
There were also lots of different types of granite. Despite what your counter top may be made of, granite is an igneous rock that is made up of large crystals of similar sizes. The composition of granite is high in silica, so you get lots of quartz and feldspar.
|The abundance of the pink mineral (potassium feldspar) means this column likely came from Egypt.|
|There was also lots of diorite. Diorite has a similar texture to granite, but has less silica, so different minerals.|
|Pompeii was made with a combination of basalt bricks and blocks, clay brick, and tuff.|
|A tuff is a rock made of pyroclastic material (ash, pumice, crystals and bits of broken rock) that has become lithified (i.e. is now a rock). The types of rocks I study are usually tuffs so I couldn't help but take photos of lots of them.|
|I found tuff at the bottom of the Colosseum, in the Roman Forum, Pompeii, Herculanium, old Greek theaters in Sicily and in modern banks and gelato shops.|
|Residents of Pompeii also used basalt (lava) to pave their streets. This image is of a cross walk in the streets of Pompeii. The modern cities of Sicily still use basalt blocks, but they use paint for the cross walks.|
|Any stone can be used to make a wall, and here are some pieces of scoria mixed with some chunks of coral.|
|The white squares are crystals, the brown clast is scoria and the black is a patina from ~2000 years of people and weather touching this piece of the Colosseum.|
My visit to Rome was an excellent chance to see layers of human history exposed all in one place (Greek, Roman, Medieval, Modern). It reminded me very much of the layers of rock that we use to reconstruct the history of the Earth. Seeing the walls made out of pyroclastic material in Pompeii and the pyroclastic material that buried it was a stark reminder that we have a lot to learn still about this planet, and the clues are so often right in front of, or below us.