An example of an object the size of a Millimeter (mm) is the tip of your pencil. An example of an object the size of a Centimeter (cm) is the fingernail.
Your answer depends on the cut of the stone and what about the stone you are measuring.
Objects are congruent if they are the same size and shape, or an exact reflection of one another. If objects are not congruent, they are dissimilar in either size, shape or both.
Congruent
The size of these two objects is exactly the same: 5mm.
The size of the stone used in a 2ct princess cut diamond engagement ring is 8.2mm. This size is measured using a pair of brass calipers. The size can vary, depending on how deep the diamond is, but as a guide 8.2mm is a fair estimate.
tip of your pencil
anything that is about 4inches or 10cm
A millimeter is about the same size and a dime's thickness.
an a5 bit of paper
The point of a newly sharpened pencil is one example.
A pinhead is about 1 mm across.
paper clip, a coin,an almond, a peach pit, an olive
About 1 millimeter
It is a centimeter
It is about a millimeter in diameter.
One thousandth of a meter :)
148mm