Purchase a rock tumbler and the required coarse grit, medium grit, fine grit, and polish. These items are not included with the rock collection.
Review your rock tumbler’s instructions before starting, including the recommended barrel capacity, water level, speed, and cycle times.
Check each rock for deep cracks, fragile edges, or loose pieces that could break during tumbling. Remove any heavily damaged specimens.
Photograph your raw rocks before tumbling so you can compare their original appearance with the finished, polished results.
Mineral | Mohs Hardness: 7
Amethyst is the purple variety of quartz and often forms inside mineral-rich cavities in rock. Small amounts of iron and natural geological processes produce its purple color.
AFTER TUMBLING: Rounded edges and a glossy surface that highlights its lavender-to-violet coloring.
Mineral | Mohs Hardness: 7
Tiger’s eye is a variety of quartz known for its golden-brown bands. Its fibrous internal structure produces a shifting reflection called chatoyancy.
AFTER TUMBLING: A smooth, silky finish that makes its golden color and reflective bands more noticeable.
Mineral | Mohs Hardness: 6.5–7
Green tree agate is a variety of chalcedony featuring green, branch-like mineral patterns. These natural markings often resemble trees, moss, or other plant life.
AFTER TUMBLING: A smoother surface that makes the stone’s green patterns clearer and more colorful.
Mineral | Mohs Hardness: 6.5–7.5
Garnet is a group of minerals that commonly forms when existing rocks are changed by intense heat and pressure underground. Garnets occur in several colors, although deep red is the most familiar.
AFTER TUMBLING: A smoother surface with deeper red tones that may become easier to see under bright light.
Igneous | Mohs Hardness: 6–7
Diorite forms when molten material cools slowly beneath Earth’s surface. This slow cooling allows its light and dark mineral grains to grow, creating its recognizable “salt-and-pepper” pattern.
AFTER TUMBLING: Rounded edges and a clearer speckled pattern. The amount of shine may vary between specimens.
Metamorphic | Mohs Hardness: 7
White quartzite begins as quartz-rich sandstone. Heat and pressure beneath Earth’s surface fuse the quartz grains together, creating a hard and durable rock.
AFTER TUMBLING: A smoother surface with a subtle glassy or crystalline shine.
Igneous | Mohs Hardness: 6–7
Pink granite forms when magma cools slowly beneath Earth’s surface. Its pink color typically comes from feldspar, while quartz and darker minerals create its speckled appearance.
AFTER TUMBLING: A smooth finish that makes its pink color and contrasting mineral grains more noticeable.
Mineral | Mohs Hardness: 7
Quartz is one of the most abundant minerals in Earth’s crust and is found in many types of rocks worldwide. It often forms when mineral-rich fluids cool inside cracks underground.
AFTER TUMBLING: Smoother edges and a glass-like shine. Natural fractures or cloudy areas may remain visible.
Follow the amethyst through each stage to see how its shape and finish change along the way.
Grit gradually removes material as the rocks tumble. Some reduction in size is normal, especially during the coarse-grind stage or when a specimen has softer areas and natural fractures.
Rocks with similar hardness can generally be tumbled together. Softer specimens may wear down faster or be scratched by harder rocks, so inspect the batch between stages.
Yes. Completely clean the rocks, barrel, lid, rim, and other components before adding the next grit. Even a small amount of coarse grit can scratch rocks during the polishing stages.
No. Rock-tumbling slurry can settle and harden inside pipes. Allow it to dry and dispose of it with household trash, following any applicable local disposal guidelines.
Not necessarily. Every specimen is naturally different, and the final color, shape, size, pattern, and shine will vary. Some rocks also polish more evenly than others.
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Ten rock and mineral specimens pair for matching-game gameplay in introductory geology classrooms targeting hands-on identification skills.
PLEASE NOTE: This set includes the rocks for tumbling only. A rock tumbler, grit, and polish are not included.
