Roman Breccia Famous Building Stone ID'd

This video features a sedimentary building stone called Roman breccia. This breccia originates from Baixas, Pyrenees-Orientale, France (near the border with Spain). Breccia stone is well known in European architecture. The Romans considered breccia a precious stone, and often breccia was featured in various "high-profile public buildings". Many breccia quarries are in southern France or Northern Italy (although other quarries were located elsewhere). Breccia also was used in prominent buildings and sculptures by ancient Egypt and in the Minoan palace of Knossos on Crete [Reference: en.wikipedia.org/wiki/Breccia].
The building stone industry classifies rocks into fewer lithic categories than in geology. It should be noted that a breccia in architectural terms often is called marble. It is because many of these breccias are dominated by either marble or limestone rocky components (although many are not). Marble is much easier to cut and carve than harder stones (especially in ancient times when hardened tools were limited to non-existent).
The main way to geologically differentiate breccia and conglomerate is by determining the dominant rock type within. Usually a variety of rock shapes are within both breccia and conglomerate rock types. However, the rock name mostly is based on the dominant shapes of the rocks within--either angular or rounded (note: rock name is not based on the exterior shape of the entire rock--only by the rock shapes within).
A breccia is a rock that is made of angular-shape rocks--that are within the whole rock (rock shapes have pointed, angular exteriors--boxy shapes, triangular shapes, and splintery-shapes). In contrast, a conglomerate is made of mostly rounded rocks--spheroidal shapes, oval shapes, and rounded disc-shape rocks. Some of both angular and rounded rocks often are in either breccias or conglomerates. But the proportionally dominant rock shape generally determines the breccia or conglomerate rock name.
Breccias tend to form from rock falls and debris flows (although breccia can form in other ways too). The rocks within breccias are dominantly angular because the rocks have not travelled far from the source area. Therefore, the individual rocks have not been subjected to much rounding by tumbling and abrasion and wear. Breccias also tend to be matrix-supported rocks (poorly sorted). This means that the angular rocks within, are generally separated--and less likely to be in direct contact with adjacent rocks (located within the rock). The angular rocks are mostly well separated by sand-size or- mud-size particles. Limited travel distance also limited the sediment sorting.
It is interesting that this Roman breccia is rock-dominated, with minimal amounts of smaller-size matrix materials between the angular rocks. The rocks are essentially touching each other, and often appear to fit together like a jigsaw puzzle. The rocks within this specific Roman breccia once were in some type of scree-size talus slope.
In contrast, conglomerates tend to form in either river channels or along wave-exposed beaches. The constantly moving water in these environments tend to wash away the sand-size and mud-size particles (which are smaller than the surrounding rounded-shaped rocks). The relatively constant water movement in these environments, also provides a moderate amount of sorting to the gravels (the rocks mostly are within a range of similar sizes). Therefore, conglomerates tend to have much better sorting than breccias. Additionally, conglomerates tend to be more clast supported (compared to matrix-supported breccias). Also, the rounded-shaped rocks in conglomerates tend to be in direct contact with adjacent rocks. Note: the relatively large pore-spaces (located between rocks in a conglomerate), can create lower energy localities, which may allow collection of sand-size particles (within the pore-space localities). But the sand within conglomerates do not create a matrix-dominated rock.
Hello Rock People! This is Dave the Geology Dude! Identification notes for this rock are below in this text. Please be aware that the only way to really learn rock identification, is to have hands-on experience. This is because visual experiences alone do not show properties like hardness, acid reactivity, density, and the range of variables that are common to each rock type. Don't forget that Geology isn't rocket science--it's Rock Science! Please "like" and subscribe to this CZcams channel!
Music (CZcams Audio Library): Invisible Pieces (by Silent Partner)
Copyright by David Knoblach, 2023. All rights reserved

[@GeologyDude]

Hello Rock People! This is Dave the Geology Dude! There is more to this video than just a spinning rock. There are detailed notes in the description area of this video. If you want more, longer length rock identification videos are on my CZcams homepage. Check them out, or leave a comment here!

[@mafic_taco7061]

That is one beautiful Roman jigsaw puzzle you got there!

[@GeologyDude]

Yes, this is an awesome sample that someone gave me years ago.

[@karenlyn8592]

❤