Clarity

Most diamonds seem completely transparent to the naked eye. In fact they often contain inclusions — crystals, feathers, clouds — so slight that they are visible only with a loupe. Think of them less as flaws than as a signature. A diamond crystallises over an immense span of time, under heat and pressure that shift as it grows; wherever those conditions waver, the carbon traps a tiny witness to the moment. Clarity is simply the reading of those witnesses at ten-times magnification.

The clarity scale

Grade	Name	What you see
FL · IF	Flawless · Internally Flawless	No internal features; at most minor surface marks
VVS1 · VVS2	Very, very slightly included	Minute inclusions, very difficult to see even with a loupe
VS1 · VS2	Very slightly included	Minor inclusions, difficult to somewhat easy to see
SI1 · SI2	Slightly included	Noticeable under the loupe; SI2 sometimes visible to the eye
I1 · I2 · I3	Included	Visible to the naked eye, increasingly affecting brilliance

A stone that shows nothing at all — no inclusion, no surface mark — sits at the summit of the scale, and such stones are uncommon. GIA records them as Flawless: no internal or external features under the loupe, bar a few permitted naturals. The IDC reaches the same point by another name and calls it Loupe Clean.

A grader’s method

Inclusions are described by where they sit and what they are — pinpoints and clouds, feathers and fractures, naturals left on the girdle, growth and twinning lines. The difference between, say, VVS1 and VVS2 comes down to the size, position, brightness and number of those features.