The red flecks in strawberry quartz are mineral inclusions inside the quartz rather than a colouring of the quartz itself, which is why the stone reads as pink with pepper. The inclusions are usually iron oxide; the body colour comes from a separate, finer dispersion.
Because the inclusions are irregular, a strand will always have some beads that are nearly clear and some that are heavily flecked. That unevenness is the material. A strand with perfectly even speckling throughout is generally a glass imitation.