Crystals, gems, minerals, rocks: people often use these terms interchangeably, but each category has important technical differences. Let’s take amber, for example. Some people refer to amber as a crystal, but amber actually comes from fossilized tree resin. Later, I will explain why people can still consider it a gem.
Many factors determine what the Earth will spit out. It all depends on depth, pressure, temperature, location, chemical composition, and more. The Earth really has many surprises, so let’s get this geological show on the road!
Crystals, Gems, Minerals, Rocks: How They Differ
These four categories can overlap, which is one reason the terminology gets confusing. A single specimen may qualify as a crystal, mineral, gemstone, rock, or more than one of these at the same time. The difference usually comes down to how it formed, what it contains, and how people value or use it.
How Crystals Compare With Gems, Minerals and Rocks
A crystal is a solid with an organized, repeating internal structure. Many crystals are minerals, but not everything with a crystal structure qualifies as a mineral.
Here in Minnesota, we celebrate our famous Lake Superior Agate. Agate is a banded variety of chalcedony, which is a microscopic crystalline form of quartz.
People can consider a Lake Superior agate a gemstone. Because it also consists of a naturally occurring mass of mineral material, geologists can call it a rock. I know, your mind is blown!
What Is a Gem?
A gem, or gemstone, can be a mineral, rock, or organic material. People usually value gems for their beauty and often for their rarity or durability. People commonly cut and polish gems, especially when they use them in jewelry or decoration.
Let’s take a diamond, for example. A diamond is both a mineral and a crystal. When people value it for jewelry, they also consider it a gemstone, a very expensive one!
Now, let’s go back to amber. As I previously stated, amber comes from fossilized tree resin. Unlike a diamond, amber is an organic substance. Gemologists consider amber a gemstone, but not a mineral, crystal, or rock.
Lots to remember, I know, but stay with me! We only have two more to go.
What Is a Mineral?
A mineral is a naturally occurring, inorganic solid with a specific chemical composition and an ordered internal structure. Gemologists classify opal as a mineraloid rather than a true mineral because it lacks an ordered crystalline structure. Opal can qualify as a gemstone, but not as a true mineral or crystal. Other mineraloids fall into this category as well.
What Is a Rock?
A rock is a naturally occurring combination, or aggregate, of one or more minerals, mineraloids, or organic materials. I chose marble as an example because most of us recognize it from marble countertops.
Calcite or dolomite makes up most marble. Heat and pressure transform limestone or dolostone into this metamorphic rock over time.
Why Crystals, Gems, Minerals and Rocks Can Overlap
Just like most things, learning about geology takes time. Time also plays a big part in the formation of many rocks, minerals, and crystals that eventually become gemstones.
The next time you pick up a beautiful stone, crystal, or gemstone, remember that what you are holding may be a lot more complicated than it looks. Sometimes, one specimen can fit into more than one category, which is exactly why these terms get so confusing.
Every Stone Has a Geological Story
Whether it is a Lake Superior agate, a piece of marble, a diamond, or even amber, each one has its own story about how it formed and what it contains. That is one of my favorite things about geology. Something that looks like “just a rock” can actually tell us a story that took millions of years to create.
Understanding crystals, gems, minerals, rocks makes every specimen even more interesting. To see more examples, browse our collection of crystals and polished stones.
If someone calls everything shiny a crystal, you can smile and know that there is a whole lot more to it than that. After all, not everything that glitters is gold, and not everything that sparkles is a crystal!