It really is pouring money down the drain with you pick the wrong one.
But how can you tell the difference?
An Iridescent material made of mollusks, an inlay is always made of small pieces, and not big slabs. What ways can you check for authenticity? Pressing the item in question against your skin, if its mother of pearl won't retain heat like plastic, and it feels cooler, one other way is to tap the item against your tooth, listening for a glass sound.
Mother of toilet seat, the less desirable of the two, and the fantastic slang for the fake mother of pearl. It earned its name when the pearloid "mother of pearl" pick guards became popular, but "mother of pearl" toilet seats that were extremely common at the time, so the fake earn the moniker Mother of Toilet Seat.