Heart

The heart is the hardest shape to cut well and the easiest to get wrong. Everything depends on symmetry: the two lobes must match in height and roundness, the cleft between them must be sharp and centred, and the point must fall on a straight line through the middle. Miss any of it and the stone stops reading as a heart and starts reading as a mistake.

Size matters more here than anywhere else. Below about half a carat the outline becomes difficult to resolve at arm's length, and much of what makes the shape worth choosing is lost. It wants room to be recognised.

The point carries the same vulnerability as a pear and wants the same protection. The cleft is where cutters lose stones, and where a well-cut heart shows its quality.

What it offers in return is directness. There is no shape that states its meaning more plainly, and no shape that requires more confidence to wear. It resists subtlety, so attempts to make it understated usually fail. A simple solitaire on a fine band, letting the outline carry everything, is almost always the right answer.