You can often spot filled diamonds with a 10 power loupe, but using a binocular microscope is easier. In most states, it is against the law to sell you a treated diamond without first telling you.

You would need a jeweller's loupe the size of the Sun to grade this diamond.

Each usually comes with a diagram, marking the position of the tiny specks of carbon that can be seen when viewed through a "loupe", the jeweller's 10x magnification tool.