How can I see inclusions in a diamond with my naked eye?

Seeing inclusions in a diamond with your naked eye is harder than most people expect, and that's not a problem with your eyes. A stone has to be fairly included. In my bench, clients bring in SI1 and SI2 stones and expect to spot something. They almost never can without a 10x triplet, even when I point exactly where the inclusion sits.

Start with a clean stone and side light

To actually see inclusions, start with a clean stone. Grease and lotion scatter light and hide what's inside, so wash the diamond in warm water with a drop of dish soap and dry it with a lint-free cloth. Then set the diamond table-down on matte black paper or a dark cloth. Shine a bright LED phone flashlight from the side, not straight down. Look through the pavilion and tilt it slowly. Inclusions show up as small dark specks, whitish feathers, or a faint haze. Reflections do too. Change the angle.

What you're most likely to spot this way: black carbon spots, included crystals, large feathers near the girdle, maybe a milky cloud if the clarity grade is low enough. In a stone graded I1 or lower, a dark inclusion under the table can be visible face-up from across a room, which is why jewelers argue about whether I1 belongs in an engagement ring at all. In an SI2, you might catch it only from the side with effort. In an SI1 or better, forget it. That's why the term eye-clean means nothing until you know the distance, the lighting, and the person doing the looking.

If the stone came with a GIA report, use the clarity plot because it gives you the exact position and type of every inclusion, and lining that plot up with the stone under a desk lamp teaches you what a feather actually looks like. A feather isn't a void. It's a tiny break that catches light differently and often appears as a faint white line when you tilt the stone against a dark background.

One caution: do not breathe on the stone and squint into a jewelry store's halogen spotlights. That shows you reflections, not inclusions. And if you have to work this hard to find it, nobody at a dinner party ever will.