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Smithsonian Crystal Growing Geodes Review

Diamond and Amethyst Crystals

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You can make your own geode using plaster of paris, alum, and food coloring.

You can make your own geode using plaster of paris, alum, and food coloring.

Anne Helmenstine
You can grow 'frosty diamonds' and 'purple amethyst geodes' with the Smithsonian Crystal Growing Geodes kit. Here's my review of this popular crystal growing kit.

Description of the Geode Kit

Natural geodes are hollow rock formations that contain deposits of crystals. If you can't wait a few million years for a natural geode to form, you can make one yourself using common ingredients or a crystal geode kit, such as the Smithsonian Crystal Growing Geodes Kit. The Smithsonian kit includes materials to grow three crystals. You can grow 'frosty diamonds' and two 'purple amethyst geodes'. The kit is intended for kids ages 10 and up.

What You Get and What You Need

You get everything you need to grow the crystals and geodes except hot water. The kit includes:

  • instructions
  • pamplet about natural geodes and crystals
  • goggles
  • plastic growing cups
  • plastic geode mold
  • bag of plaster sufficient for 2 geodes
  • 2 wooden spatulas
  • monofilament thread
  • measuring cup
  • magnifying glass
  • granite base rock
  • chemicals for growing clear and purple crystals
What You Need
  • hot and boiling water
  • may want separate containers for mixing ingredients

My Experience with the Crystal Geodes

In the Smithsonian kits, these are called 'frosty diamonds'.

In the Smithsonian kits, these are called 'frosty diamonds'. The crystals are alum on a rock.

Anne Helmenstine
The instructions are a little wordy, so I decided to try the simpler crystals first: frosty diamonds. Basically all you need to do to make these crystals is dissolve the 'diamond' powder in hot water, pour the solution over a rock that you have placed in a growing cup, and collect your crystals the next morning. It was that easy! These turned out beautifully. Be sure to save a few small crystals for the geodes.

The kit contains materials for making two 'amethyst' geodes. You will need to make the geodes one at a time, since there is one mold for making the plaster 'rock'. You can add a couple of small crystals from the frosty diamonds project to help seed the crystals that will grow on your geode, though it isn't absolutely necessary to have any leftover crystals from that project. The geodes turned out very nice, though I did not get the bright purple coloration that is shown on the package photograph. The color is absorbed into the geode, not incorporated into the crystals, so I'm not sure how you would get deeply-colored crystals. They still look great, just maybe not what you would expect based on the packaging.

Pros and Cons

Pros
  • highly reliable results
  • crystals are nice enough to keep as specimens
  • complete kit - no hard-to-find extras required
  • safe educational project for kids
Cons
  • instructions are a bit hard to follow
  • though the frosty diamonds looked just like the photo on the box, I think it is unlikely you will get geodes that look the same
  • obviously, you aren't growing diamonds or amethysts, but I think the packaging should be a little more clear about that

The Bottom Line

This is my favorite Smithsonian crystal kit because the crystals grow reliably and I think the resulting crytals and geodes are very beautiful. You can put them in display cases and keep them for years. The materials and instructions are safe for kids. The pamphlet provides enough background that the kit is educational without being overwhelming. I'd recommend this kit for anyone who enjoys growing crystals.

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