The mini tile assortments are a great way to get a range of colors for a small project at a low price. However, it isn't always possible to identify a tile contained in the assortment because they contain some colors in addition to the standard ones we carry. For that reason, you should not buy an assortment as a means of finding one particular color that you might want more of. Buy samples instead.
3/8-Inch Mini Vitreous Glass Tile Assortments
The assortments come in 1-pound bags of approximately 640 tiles, which should cover about 0.85 square feet assuming a standard grout gap of 1/16".
Make sure you order enough for your project before you start gluing tile down, which is standard advice for all mosaic work because tile varies by manufacturer batch, including the most expensive Italian brands.