Science Questions with Surprising Answers
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Dr. Christopher S. Baird

Why are crystals rare?

Category: Chemistry      Published: March 15, 2013

By: Christopher S. Baird, author of The Top 50 Science Questions with Surprising Answers and Associate Professor of Physics at West Texas A&M University

sand dunes
Ordinary sand is the exact same thing as large quartz crystals used in jewelry. Both are made out of silicon dioxide crystals. The only difference is that the quartz use in jewelry is large enough for humans to notice its beauty. Public Domain Image, source: U.S. National Park Service.

Crystals are in fact very common. Take a look around you when you sit down to dinner. Your metal knife is a crystal, as are your spoons, forks, and metal serving bowls. The ice in your cup is a crystal, as is the salt in your shaker. Your ceramic plates and bowls are also crystals. Interestingly, your "crystal" wine cups are actually one of the few items in your house that are not crystal. Looking into the kitchen, you see your metal fridge, your metal sink, your granite counter tops, your tiled floor, your plaster walls, and your electronic gadgets – all crystal. In fact, aside from glass and organic material such as wood, cotton, or bamboo, almost all solids are crystal. There are even some liquids that are crystal, such as in your iPod screen. In science, the word "crystal" describes a material that has an ordered spatial arrangement of its molecules. For instance, salt molecules line up in straight columns and rows when forming a salt crystal. Almost all metals, ceramics, salts, rocks, and semiconductors form crystals when in the solid state. Glass, on the other hand, has its molecules randomly distributed. Organic materials such as wood and cotton have highly complex biological structures on the molecular level and therefore do not have the simple repeating patterns characteristic of crystals. But simple organic molecules, such as sugar, do form crystals if they are concentrated and solidified.

The word "crystal" is used in popular culture to refer to an object that should be more accurately described as a "pretty crystal". The only difference between quartz drops hanging from expensive chandeliers and sand thrown out on the streets is that the chandelier drops are big and pure enough to be pretty. Both are made of silicon dioxide crystals. When the average person says "crystal", they mean "pretty crystal". Unfortunately, society's obsession with the prettier instances of crystal has lead to the belief that only pretty crystals are crystal. Trying to tell a friend that the copper wires in her lamp cord are just as crystal as the diamond on her finger may illicit stares of disbelief because copper wires aren't pretty. This fascination with the beauty of certain crystals has even lead to belief in the healing power of crystals. The belief that crystals can give humans energy or healing power is nonsensical and unscientific. If the sparkly chunk of calcite in your hand can heal you because it's a crystal, then so can your fridge or your sink because they are also crystals. If beautiful quartz gems can give you energy, then so can the sand you use to clean up oil spills in the garage. They are both made out of the exact same thing: crystallized silicon dioxide. Psychologist Christopher French carried out numerous controlled experiments with pretty crystals where he found that they had no healing power or energy effect at all. He used genuine pretty crystals and phony copies made out of regular glass. He then gave these items to various believers and non-believers in crystal healing to see if they could tell the difference between the real crystals and the fakes. If crystals emit human energy, then people should be able to detect the real items from the fake by sensing this energy. Dr. French found that both groups of people could do no better than random chance at detecting the real crystals from the fakes.

As should now be evident, crystals are not rare. But pretty crystals seem to be rare. Why? The answer is twofold: erosion and mixed composition. Wind, rain, and water flow have a way of knocking and mixing around things here on earth. This erosion causes big crystals such as a palm-sized amethyst to get knocked apart into little crystals. The result is sand, silt, and clay. The earth is covered with sand, silt, and clay as opposed to being covered with giant gem-quality crystals partly because of erosion. Also, when rocks are forming inside the earth, a mixed composition means that crystals of one material get in the way of the crystals of another material while they are forming. As a result, the crystals end up small. For instance, solid granite is a mixture of small quartz, mica, and feldspar crystals. The specks of grains you see in granite are the individual crystals.

Topics: amorphous solid, crystal, gem, glass, metal, quartz