Gemstone clarity refers to the degree to which inclusions (tiny imperfections) are present.
The occurrence, type, and acceptability of inclusions varies from gemstone to gemstone. Emerald, for instance, tends to contain visible inclusions and can still be valued highly despite this.
Unlike for diamonds, there is no standard grading scale for colored gemstones. Fewer flaws generally translates to higher prices, though there are some cases in which specific flaws actually increase value. One example of this are horsetail inclusion in green demantoid garnet.
The clarity of a colored gem must be compared to what is standard for that variety. Aquamarine, for instance, naturally tends to contain fewer inclusions than ruby.