Tag Archives: salt

Make a Salt Crystal Geode

Salt Crystal Geode

Food coloring stains the eggshell of the geode rather than the crystals. (Anne Helmenstine)

It’s easy to make your own crystal geode using an eggshell and salt, plus it takes a lot less time than waiting for Mother Nature to make a geode.

About Geodes

Geodes are natural rock formations that often take millions of years to form, as minerals crystallize in cavities in the stone. The kind of geode you can make still consists of minerals, but it takes a lot less time to grow the crystals.

Salt Crystal Geode Materials

  • salt (table salt, rock salt, Epsom salts, etc.)
  • boiling water
  • food coloring (for colored crystals)
  • eggshell
  • small bowl

Make the Geode

A natural geode forms when crystals deposit inside another mineral. Your mineral is the calcium carbonate of an eggshell.

  1. To get the base for the geode, crack open an egg, remove the egg, and keep the shell. Rinse out the shell and let it dry.
  2. Find a small bowl or cup that is bit larger than your eggshell.
  3. Boil enough water to fill the bowl. An easy way to do this is to fill the bowl with water, empty the water into a glass measuring cup, and microwaving the water until it boils.
  4. Make a saturated salt solution. Stir salt into the boiling hot water until no more salt will dissolve. You’ll know you have a saturated solution when a few crystals remain at the bottom of the container. The solubility of salt depends on temperature, so it’s best to use boiling hot water.
  5. If you want colored crystals, add a few drops of food coloring to the solution.
  6. Place the eggshell in your container. Pour the salt solution into the shell. It will overflow the shell, which is fine. Pouring the solution into the shell keeps it from floating.
  7. Crystals will start to form as the solution cools and water evporates out of the container. You may get good crystals overnight or it may take a couple of days to see good growth, depending how saturated your salt solution was.
  8. When you are pleased with the crystals, remove the geode from the liquid and place it on a paper towel to dry.
  9. Display your crystal geode or wrap it in paper if you wish to store it. You can dust it, but don’t expose it to water or your salt crystals will dissolve.

Grow Table Salt or Sodium Chloride Crystals

Table Salt Crystals (Choba Poncho)

Table Salt Crystals (Choba Poncho)

Table salt or sodium chloride crystals are among the easiest crystals to grow. The materials are easy to find and inexpensive, plus the crystals are non-toxic.

Crystal Growing Materials

  • table salt – sodium chloride – NaCl
  • water
  • clean clear container
  • piece of cardboard (optional)
  • string
  • pencil or butter knife (optional)

Salt Crystal Step-By-Step

  1. First you need to prepare a saturated salt solution. Stir salt into boiling hot water until no more salt will dissolve. Salt may settle out at the bottom of the liquid. This is fine – just make sure none of the undissolved salt gets into your crystal-growing container. Be sure the water is as close to boiling as possible. Hot tap water is not sufficient for making the solution. If you want colored crystals, you can add some food coloring to this solution.
  2. If you want crystals quickly, you can soak a piece of cardboard in this supersaturated salt solution. Once it is soggy, place it on a plate or pan and set it in a warm and sunny location to dry out. Numerous small salt crystals will form over the span of a couple of hours.
  3. If you want a mass of crystals, you can simply pour the saturated salt solution into a clear container and let it slowly evaporate. Crystals will grow on the sides of the container.
  4. If you are trying to form a larger, perfect cubic crystal, you will want to make a seed crystal. One way to get a seed crystal is to pour a small amount of saturated salt solution onto a saucer or watch glass. As the liquid evaporates, crystals will start to form. Select a single square crystal and remove it from the dish.
  5. To grow a big crystal from a seed crystal, carefully pour the supersaturated salt solution into a clean container (so no undissolved salt gets in), allow the solution to cool, then hang the seed crystal in the solution from a pencil or knife placed across the top of the container. The solution needs to be saturated and cooled so that it won’t dissolve your seed crystal. You could cover the container with a coffee filter or paper towel to keep out dust, yet permit evaporation.
  6. Set the container in a location where it can remain undisturbed. You are more likely to get a perfect crystal instead of a mass of crystals if you allow the crystal to grow slowly (cooler temperature, shaded location) in a place free of vibrations.

Crystal Growing Tips

  • Experiment with different types of table salt. Try iodized salt, uniodized salt, sea salt, or even salt substitutes. Try using different types of water, such as tap water compared with distilled water. See if there is any difference in the appearance of the crystals.
  • If you are trying for the ‘perfect crystal’ use uniodized salt and distilled water. Impurities in either the salt or water can aid dislocation, where new crystals don’t stack perfectly on top of previous crystals.

Learn More

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