Every mineral has its very own special crystal formation. But what are minerals and what are crystals? Let us know more about it.
What are Minerals
Geologists and scientists who study the earth agree that a substance must meet all five of these to be considered a mineral.
It must be naturally occurring, solid, Inorganic, a fixed chemical formula, and an ordered crystalline structure. Let’s look at what each item means?
Naturally-occurring
It means that it is not made by a person. Like a table is not naturally occurring because it is constructed by a person. But the wood used to make the table is naturally occurring because it comes from nature.
Does wood make a mineral though? Not so fast. Remember that a substance needs to meet all five criteria.
Solid
When it is at room temperature wood is solid. Can wood be a mineral now? Not yet. We haven’t looked at the next three items on the list.
Inorganic
Inorganic means that the substance is not made by an organism or a living thing. Wood is made from a tree and a tree is an organism and living thing. So wood is definitely not a mineral. Now we get into a little chemistry.
Fixed chemical formula
Having a fixed chemical formula means that the mineral has the same chemical makeup each time. For example, the mineral quartz is made up of silicon and oxygen atoms.
Atoms are the basic tiny particles that make up all matter. When atoms join together, they can become molecules, but atoms cannot be divided into smaller parts.
So every time that silicon and oxygen atoms combine in this form which is a fancy chemistry formula, shows one atom of silicon and two atoms of oxygen.
Ordered crystalline structure
It means that the atoms that make up the mineral have a pattern. Don’t worry, if the chemistry of minerals sounds confusing to you, you can still enjoy rocks and their minerals by how they look and feel. It’s really important to organize them into categories.
There are eight common groups of minerals. Native elements, sulfides, oxides, phosphates, sulfates, carbonates, halides, and silicates.
Whereas most minerals are made up of several chemical elements, minerals are considered to be mated elements. Copper iron and graphite are considered to be native elements and are very commonly found.
Gold, platinum, and silver are considered to be rare native elements. However, Sulphur and carbon are examples of nonmetallic native elements. Sulfides are made up of sulfur plus another mineral usually a metal mineral.
This group is known to be heavy, brittle, and metallic-looking. Other sulfides are Galena, cinnabar and stibnite. Oxides are minerals combining metal and oxygen.
Hematite is often used in making jewelry and is also really great for meditation. Other oxides are magnetite, cuprite, and corundum. Phosphates are minerals made with phosphorus and oxygen.
There are actually over 200 phosphates. The most common ones are turquoise and apatite. Phosphate minerals are often used for fertilizer, but also as preservatives in food and cosmetics.
Sulfates are made of sulfur, plus oxygen and metal. It is a soft mineral and often translucent, which means it allows light through it. Even if we can’t see through it clearly like glass.
Also read: Chemical composition of minerals
Some examples of sulfates are gypsum, barite, selenite, celestite, and anhydrite. Carbonates are a combination of carbon, oxygen, and metal. Examples are calcite, rhodochrosite, and malachite.
This group of minerals is so soft that they dissolve with mild acids like vinegar. Halides are made by combining metal and one of these elements – Chlorine, bromine, fluorine, iodine, or astatine. Some of which dissolve in water.
Halides rock salt is one example. Can you guess what Halides is used to make? That’s right table salt. Fluorite and sylvite are other examples of halides and finally silicates. Silicates are the largest group of minerals and are made of oxygen and silicon.
Quartz is the most common in this category. But so is amazonite. Muscovite, mica, and of course silicon. Other minerals in this category are biotite, labradorite, talc, and olivine. When lava from a volcano cools, the liquid particles come together and harden creating a chemical bond.
Read: Difference Between Minerals and Crystals?
Crystals begin to grow. This means that they make up atoms and molecules. These minerals are organized in a special way by a repeating pattern. Crystals don’t only form from lava.
However, they often form from a liquid when it starts to harden. Ice is an example of a crystal that forms when a liquid hardens. But another way crystals form is when water evaporates from the mixture like saltwater. When salt water evaporates it makes salt crystals.
Snowflakes are crystals that form when water freezes. I bet you didn’t know that many computer screens are made with liquid crystals. Crystals can be cubic, with a square structure like diamonds, hexagonal with a six-sided structure like emeralds, trigonal with a triangular structure like quartz, and monoclinic which has a parallelogram structure like azurite.
Orthorhombic is based on a rhombus or a diamond shape like celestite, tetragonal which has a rectangular structure like zircon, and triclinic which has random shapes like labradorite. As you can see crystals can also be blue or purple or green or yellow or black or a combination of so many colors. Just like everything in science.
There are some exceptions to the classification rules. For example, coal is a sedimentary rock and it’s made with plant particles or organic substances. It is also considered a mineral even if the rule of a mineral is made from inorganic substances.
Geologists don’t agree on the classification of coal. So you might see it classified as both a rock and a mineral. There are other tricky classifications that you may find as you study rocks and minerals more closely.
For instance, How would you classify salt and sugar? Salt is considered to be a mineral as we know, but sugar is not. Remember that in order to be a mineral the substance cannot be made from a living organism.
Since sugar is made from plants, sugar canes, and sugar beets, it is not a mineral. Even if it has crystals. When a crystal is so beautiful, it can be cut and polished. It is called a gemstone or gem for short. Gems come in a variety of beautiful colors, shapes, and textures.
They are often used to make jewelry. Diamonds, emeralds, rubies, and sapphires are examples of popular gemstones used for jewelry. Some other crystals that are often turned into gemstones are amethyst, amber, opal, pearl topaz, and many others.
Crystals and gemstones are so beautiful that many people like to collect them.