Most rock advent calendars are 24-day countdowns that reveal one gemstone or activity each day.
They commonly focus on geology and general science, offering mineral identification, STEM-style activities, and hands-on experiments in some sets.
Calendars often include a mix of formats: raw or rough stones, polished/tumbled stones, crushed or chip pieces, and sometimes small bottles or chip strands (beads with holes) for stringing.
Many calendars come in a reusable tabletop box or include a collector’s pouch or storage bag so specimens can be kept together and displayed or stored after the countdown.