This EarthCache is just outside Glasgow Central Station, namely on Hope Street. You are here to look at the stone panels to the side of 95 Hope Street.
So, what are we looking at? Well its breccia. So, what is breccia?
Breccia is a rock formed by pieces of other rocks, known as clasts, which are then cemented together in what is known as a matrix. Imagine a collection of different broken biscuits held together by chocolate - that is a matrix. In the case of breccia, the matrix is formed by a natural cement. Brecciais composed largely of angular fragments (whereas conglomerates contain rounded clasts).
Breccia can be formed by a variety of ways :
Consolidation - such as the collection of material at the bottom of steep slopes.
Cataclastic -during the process of faulting.
Volcanic - composed of ash and chunks of lava.
Hydrothermal - caused by fluid fracturing the rock mass.
Impact - from when a meteor hits the ground, it fractures the rock at the impact site.
Classification :
Matrix supported - where the clasts do not connect with other, and the matrix surrounds each clast.
Clast supported - where the clasts touch other, and the matrix fills the holes.
As can be seen, the breccia here has a myriad of quartz veins. Quartz is a common mineral, formed when silica rich hydrothermal fluid penetrates a rock.
This being an EarthCache, in order to log it, I ask that you answer some questions. Please send them to me, and do not include them in your log. You can send them to me by using the message facility or email, both of which can be found by looking at my profile.
1. Please describe the predomont colour of the breccia.
2. Is the breccia, matrix or clast supported?
3. Look closely at the quartz veins what colours can you see?