When evaluating its appearance, you have to focus on its color, clarity, and cut. Yet when it comes to the structure of the gemstone, there are plenty of chemical and physical aspects, on which faux diamonds differ from one another. In fact, the same goes for a diamond, so it is pointless to evaluate all of those characteristics of imitation stone. So you should rather focus primarily on its hardness.
Color is also one of the main quality characteristics of a faux diamond. Generally, colorless gemstones are considered more valuable than their colored counterparts. So, when selecting a faux diamond, you should go for diamond simulants with as slight color as possible.
You can get a number of gemstones that are very nearly colorless and can be used as diamond imitations. They include cubic zirconia, moissanite, white sapphire, spinel, synthetic garnet, and zircon, to name some of the most common ones. However, not all of them are perfectly colorless.
For instance, most moissanite gems have yellowish hues, which can more or less be noticeable depending upon the stone. In fact, a faux canary diamond ring is one of the popular option these days. Still, in case you wanted a whiter diamond simulant, white sapphire or cubic zirconia would be a relatively better choice.