API Sand (physical description)
Particles in a drilling fluid that are too large to pass through a 74 μm sieve (API 200 screen). NOTE 1 Its amount is expressed as a volume fraction (percent) of drilling fluid. NOTE 2 Particle size is a descriptive term; the particles can be shale, limestone, wood, gold or any other material.
Source: API RP 13C, Recommended Practice on Drilling Fluids Processing Systems Evaluation, Upstream Segment, Fourth Edition, December 2010. Global Standards