Besides sealing out moisture and insects, grout helps set the tone for a project. It all depends on how much, if any, you use. Consider these options
The stones are placed roughly a finger's width apart, leaving space for the grout to be piped between them. When the grout begins to dry, the joint is "raked" to create a concave look with consistent depth.
Boston Blend Mosaic, $14 per sq. ft.; stoneyard.com