Some common rock types as seen under the microscope.
Marble on microscope.
Rocks under the microscope.
Marble width 2 8 cm uk virtual microscope the united kingdom virtual microscope ukvm collection consists of igneous sedimentary and metamorphic rocks from around the uk.
They are shear lines caused by machines and are not true pontil marks.
Marble is a metamorphic rock that forms when limestone is subjected to the heat and pressure of metamorphism.
If the marble is completely smooth it was machine made and has no pontil marks.
Check for smooth lines or a single straight line that runs deep into the marble.