Can you tell a moissanite diamond from a diamond to the naked eye?

The conclusion is moissanite and diamonds can be distinguished with the naked eye.

Lab Moissanite has 25 times the fire colour of a diamond, so it is the moissanite that shines particularly brightly in the sun. Often moissanite will have a large red-orange fire colour, however this is rarely seen in natural diamonds.

Observe the rear faceted prongs for overshadowing: at 45 degrees, looking down the side part of the diamond table, you can see the prongs overshadowing. Two comparison pictures I took during the experiment. It is clear that, although there are many facets, the diamond prongs are clear, one by one, whereas the loose moissanite appears two by two. This can actually be seen with the naked eye, but it is more obvious with a magnifying glass.

Under sufficient light, moissanite stone has a more brilliant fire colour. Because moissanite is birefringent, with a dispersion of 0.104 picoseconds per nanometre, and diamonds are monorefringent, with a dispersion of 0.044 picoseconds per nanometre, Vvs Loose Moissanite generally reflects twice as much light as diamonds. The fire colour of a diamond is usually blue or orange, while that of a moissanite is more colourful and dazzling to the eye.