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 circumference of a circle with a 10 millimeter diameter is about 31.42 mm
tip of your pencil
A typical paperclip is about 1 millimeter in length. A grain of sand is also around 1 millimeter in size. Additionally, a staple is generally close to 1 millimeter long.
The thickness of part of a Nerf Dart
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
One thousandth of a meter :)