July 1, 2013 Leave a comment
This morning I set about to research the wine region of Priorat for a blog post. I already knew the basics of the region, such as the fact that it is one of Spain’s two DOCa wines, the main grape variety is Garnacha Tinta, and the area came to international attention in the 1990s.
Wikipedia (I know, not the best reference but in this case, just a starting point) also had this to say, “The area is characterized by its unique terroir of black slate and quartz soil known locally as Llicorella.” I already knew that the soil in Priorat is mainly Llicorella…at least I knew the word, and could have guessed it correctly on a multiple choice test. But being in a Monday sort of contemplative mood, I wondered if I really understood Llicorella. Of course, I didn’t. So I set about to deconstruct Llicorella.
First of all…just what exactly is slate? Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from sedimentary rock composed of clay or volcanic ash. It is the finest grained foliated metamorphic rock.
Metamorphic Rock? Metamorphic rocks are created from the transformation of existing rock types. Metamorphism means “change in form.” Rocks under the earth’s surface change form by being subjected to heat, generally temperatures from 300° – 400°F, which can cause both physical and chemical changes in the rock itself.
Sedimentary Rock? Sedimentary rocks are formed by the solution of mineral and organic particles within bodies of water. Sedimentation is the name for several different processes that cause mineral particles and organic particles to settle and accumulate first into a dissolved solution and later into sediment. Sediment is then transported to dry land by water, wind, or glaciers, or is left behind when the bodies of water dry up. With time, the slushy sediment hardens into rock. Sandstone is probably the most well-known sedimentary rock.
Clay? Clay is a very fine-grained soil type made up of very fine minerals such as aluminium phyllosilicates, iron, magnesium, and a bunch of other chemicals I have never heard of. The minerals that make up clay soil are the result of weathering…the breakdown of rocks, soils, and minerals through contact with air, water, and living creatures.
Volcanic Ash? Volcanic ash is made up of pieces of pulverized rock, minerals, and volcanic glass that are created during volcanic eruptions. Pieces of ash must be less than 2 mm in diameter – larger fragments are referred to as cinders or blocks. At least this one I can understand!
Foliated? There are two types of metamorphic rocks: foliated rocks and non-foliated rocks. Foliated metamorphic rocks, such as schist and slate, have a “layered” appearance that has been produced by exposure to heat and directed pressure. Non-foliated metamorphic rocks such as marble and quartz do not have the “layered” appearance.
And what is quartz? Quartz is the second most abundant mineral in the Earth’s continental crust, after feldspar. There are many different varieties of quartz, several of which are semi-precious gemstones. Quartz is the most common element of sand and sandstone and is used in glassmaking. Quartz is almost immune to weathering and is a component of granite and other igneous rocks.
Aha- that’s why sand is coarse (quartz doesn’t “weather”) and clay is fine (its made up of materials that do weather or “breakdown”).
I think I’ll stop there. But for those of you who are curious, igneous rocks are rocks that are formed by the cooling and solidification of lava or magma. Granite and obsidian are igneous rocks.
So now, when someone says, “Llicorella is a unique soil made up of black slate and quartz,” what do you know?
Sources (in addition to http://en.wikipedia.org/wiki/Priorat_(DOQ)):
The Bubbly Professor is “Miss Jane” Nickles of Austin, Texas firstname.lastname@example.org