The position of a diamond when you are looking directly down into it, from directly on top, at a perpendicular angle.
When a diamond “faces up well”, this means it looks good from the top. This is usually used to describe a diamond of an off color that looks better than expected from the top. Sometimes it is used to describe a diamond that looks larger than it is, such as “it faces up like a carat stone.” Or because of a strategic cut, it might “face up” nicely even though it has many inclusions. In other words, a diamond can face up better than it’s color grade, cut grade, or clarity grade might indicate.