If the marble is completely smooth it was machine made and has no pontil marks.
Marble on microscope.
Check for smooth lines or a single straight line that runs deep into the marble.
Lines like this as well as smooth indents or bubbles do not indicate pontil marks found on handmade marbles.
These are photomicrographs very thin slices of rock seen in plane polarised light or between crossed polarisers when the colours seen are produced by interference of light.
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.
Rocks under the microscope.