There’s a thin line visible in the stone, yet it seems to disappear when the stone is rotated. Is this a surface scratch on the table facet, a reflection of a facet junction, or an inclusion within the stone? This question is completely reasonable. Since we’re observing transparent stones, the tiny field of view includes surface reflections, inclusions, dust, and light returning from the pavilion.
To start, place the stone in front of a 10x loupe and adjust the focus on one facet edge until it’s as sharp as possible. Then, move the stone back or forth a little bit. If the line is located on the surface, it will come into focus at the same time as the facet. Generally, inclusions won’t come into focus until the surface has started to blur out. It can take some practice to get used to the small distance of movement, so try to keep your hands steady and support your arms.
The next test is to rotate the stone slowly using tweezers. A scratch will generally rotate with the facet and may reflect light only when viewed from certain angles. Dust can sometimes be removed with careful cleaning using a clean, lint-free cloth. An inclusion is always internal, although the light passing through different parts of the crown and pavilion may make the inclusion easier or harder to see. Reflections from a facet junction might seem to shift around, or multiple reflections may appear, even though the junction is stationary.
Any feature that reaches the surface requires a little more attention since the surface is the interface between the interior and exterior. Find a spot where a fracture appears to reach a facet, and then vary the lighting angle. Is there a tiny opening, a difference in luster, or a crack continuing below the surface? It’s important not to assume that all fractures reach the surface. Write down only what you can see clearly.
It’s common for inexperienced people to look at the brightest part of a feature. Sometimes, however, the brightest spots are just reflections from internal features, internal curved surfaces, or light bouncing between facets. Try focusing on something on the surface first, such as a polishing line or facet junction, and use that as your reference point. Then move down into the stone.
Your observations should use cautious language such as “thin internal line below the table” or “possible surface scratch across one crown facet” or “fracture may reach the girdle.” The goal isn’t to use location to determine the origin of a stone. Internal features don’t necessarily indicate that a stone is natural, and a fracture reaching the surface doesn’t necessarily indicate treatment.
After completing the initial inspection, it’s useful to inspect the stone again after cleaning, using a different light source. If a feature still can’t be located consistently, you should note that fact rather than trying to force a conclusion. It’s better to have a record that shows what is still unclear than to record false conclusions from a shaky loupe view.
