Stromatolite polished slice from Bolivia
Size-
13.5cm x 6.3cm x 0.7cm
Weight-
158g
You will receive the item in the photo
Because stromatolite is a biogenic sedimentary rock rock ( fossilized microbial mats) rather then a single mineral, it does not possess a single crystal system or mineral class. Its exact physical properties depend directly on the specific minerals that precipitated during its ancient formation
Hardness- 3-7 on the MOHs scale depending on wheather the composition is carbonate heavy (3) or silicifed(7)
Rock formation-
Stromatolites are formed through an organosedimentary proces. Billions of years ago,photosynthetic microorganisms mainly Cyanobacteria grew in shallow water and created sticky,mucus like biofilms called microbial mats. These mats trapped drifting grains of sand,mud and debris.
Simultaneously,the metabolic activity of the bacteria altered the surrounding water chemistry,triggering minerals to chemically precipitate right side the mat. As the bacteria grew upward towards the sunlight ,new layers formed on top of the old,bound together by mineral cement. Over vast spans of geological time,these accumulated layers lithified into distinctive,banded sedimentary rock structures.
Because stromatolite is an aggregate rock formed by environmental trapping and chemical precipitation,it does not have a single mineral class or crystal system. Instead it takes on the crystalline structures of the mineral that built it,
Carbonates-most commonly,stromatolite fall into the carbonate mineral class. They are typically rich in high magnesium calcite,aragonite or dolomite. These minerals feature original or orthorhombic crystal systems.
Silicates/oxides- over millions of years ,groundwater can replace the original carbonate minerals with microcrystalline quartz(chert or chalcedony). In other instances iron oxides like hematite or pyrite can seep into the layers,introducing Trigonal or isometric micro-crystals into the structure.
