STEM Advent Calendars

Blue Marble publishes 24 days made up of 13 experiments selected from its science kits and 11 fossils and gemstones — naming carnelian, chevron amethyst, snowflake obsidian, a gastropod, a geode and tiger’s eye — with a storage pouch and, on the final day, a pyrite specimen excavated from a mini dig brick. Rated ages 8-12.

The split is why this leads. Eleven of the twenty-four doors hand over a permanent object, which means that on 25 December the child owns a labeled rock collection rather than a memory of twenty-four afternoons. Every other science calendar here is either all experiments or all objects; this is the only one that publishes both.

The named experiments are the recognizable ones from the rest of the National Geographic range — a glowing test tube, floating coins, a crystal tree — which also tells you what the calendar is not: it is a sampler of the maker’s own kits, one day at a time, rather than twenty-four new ideas. If the child already owns the Mega Science Lab, expect some overlap.

See the full review, and rock and geology kits for where the specimen half of this leads next.

Thames & Kosmos publishes 24 experiments across chemistry, biology and physics, one per day, each daily box unfolding into a 4-page instruction manual with step-by-step directions and scientific explanations. Product dimensions 14.6 x 11.5 x 2.2 inches at 1.2 lbs, SKU 661010, released 2026, rated ages 8+.

The specification that decides this one is not the experiment count — it is the sentence about materials. Thames & Kosmos publishes that the experiments “only require additional items that are commonly found in every household”. A December calendar that needs a shopping trip on day 9 stops on day 9, and this is the only calendar here whose maker addresses that in writing.

Twenty-four for twenty-four is the highest experiment density in the category and the honest trade is that there is no residue. Buy this for a child who wants to do something each morning and the Science calendar above for a child who wants to have something.

See the full review and science experiment kits.

Blue Marble publishes 24 polished gemstones — naming agate, green aventurine, hematite, sodalite, turquenite, tiger’s eye and blue calcite — plus five jewelry settings, a collector’s pouch, and a final-day rose quartz excavated from a mini dig brick. It publishes no experiment and no age rating.

A consumable count of zero is rare enough in this category to be the whole reason to buy it. Everything else here is partly or entirely used up by the 24th; this is 24 objects that are still 24 objects in June, which is the closest an advent calendar gets to passing this site’s own test for whether a thing keeps getting picked up.

The five jewelry settings are the published after-December use and they are the reason this is not simply a bag of stones. They are also why we would hand this to a child who already has a rock collection rather than one starting from nothing — a first collection wants a geode to crack open more than it wants twenty-four polished stones.

No published age is a real gap on a product containing two dozen small stones. See toy safety standards explained and the safety note below.

Blue Marble publishes 24 days of crafts, experiments and hands-on activities including 8 magnet-backed planet models to paint, glow-in-the-dark stickers for Canis Major, Ursa Major, Ursa Minor, Orion and starscapes, a pyrite specimen excavated from an Earth-shaped dig brick, two bouncy balls to make and three celestial bodies molded with agar powder.

This is the one calendar here whose output is decoration. Eight painted planets end up on a fridge and the constellations end up on a ceiling, which is a different kind of residue from a rock collection and a better one for a child who already owns rocks.

Named constellations matter more than they look. A sticker set that specifies Orion and both Bears is a star map a child can check against an actual window in December, when those four are the easiest things in a northern sky. That turns a craft into the first use of a telescope they do not own yet.

As with the Gemstone calendar, no age is published. Treat the agar powder and paints as requiring the same supervision as any kit that mixes something.

UNGLINGA publishes 24 chemistry, physics and geology projects covering earth science and natural wonders, states that the kit comes with the necessary tools, materials and step-by-step instructions, and names growing crystals, collecting gemstones and exploring underwater currents among the activities.

It is in the lowest price band of anything on this page by a wide margin, and that is the argument for it: in a house with two or three children, one calendar each at this price is a different proposition from one calendar shared.

What is missing is published detail. UNGLINGA does not publish an age rating, and it does not publish how many of the 24 days are experiments rather than objects — the exact figure this page says to buy on. We are not going to fill either gap in; we are telling you it is a gap, which is why this sits below three calendars whose makers publish both.

For the published-age question generally, see how to read a toy box.