Minerals and Crystals

[SciBeams5Participant]

For lesson A-10 part 2 it states a crystal is always a mineral and a mineral is not always a crystal. This prompted my daughter to say “So sugar is a mineral?” We researched more and found this from Geology In: A crystal is any solid that has an organized structure. … Minerals are inorganic, naturally occurring substances that have crystalline structures. So it is a prerequisite to be a crystal in order to be a mineral. All minerals, therefore, form crystals.
Hoping someone can help us understand this more. Thanks!

[Bernard NebelKeymaster]

Thank you for your question, and revealing an error in the text, “SciBeams”. A crystal is a problematic conception. To clarify, start with visualizing atoms/molecules going from liquid to solid state. This occurs as molten materials cool or as a material in water solution comes out of solution as the water evaporates. As solidification occurs, atoms/molecules may go together in two ways. Visualize the atoms/molecules in terms of cubic building blocks. In the liquid state the blocks are in all different orientations with respect to one another, slipping and sliding about. This “random” orientation of the blocks may be maintained as solidification occurs. When this happens, the result is a non-crystalline solid. Alternatively, as solidification occurs the blocks may orient flat sides to flat sides and spaced such that each is exactly on top or beside its neighbor(s). When this occurs, the mass of cubic building blocks will form into larger cubic structures. This is the process of crystallization and the result is a crystal. Visualize how the shape of the crystal will vary with “shape” of the atoms/molecules that are involved.

Crystals are recognized by their smooth, shinny sides and sides that have specific angles with respect to one another. Crystals are most commonly minerals (inorganic), but as you have pointed out, organic compounds may form crystals as well. Sugar is an example of an organic crystal that I overlooked. The key idea to learn from all this is that many atoms/molecules, as they go into a solid state, have the tendency to orient and pack themselves together in specific ways such that masses have distinctive shapes that we recognize as crystals of given compounds. I hope this helps, but please ask further. I invite others to contribute further comments or questions.

[SciBeams5Participant]

Thank you Dr. Nebel for responding and clarifying this for me. This was a great chance to compliment my daughter for listening/asking questions and provided an opportunity to dive deeper. 🙂 Thank you. bjn

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