The second obstacle in this case, was a strong (undetected) blue fluorescence. Strong blue fluorescence and sometimes medium blue, will partially cancel yellow; a “K-L” color diamond could face up like a “G-I” color. If the stone was loose, the buyer could have simply looked into the pavilion under white light, to easily see the obvious tint of exposed yellow. (As discussed in the earlier color- grading section.) When we’re dealing in mounted diamonds, the inspection methods have to be more detailed, in order to avoid mistakes and make a reasonable profit.