What’s That Mineral?

These three crystals of the mineral quartz show how the same type of mineral can have different colors! The pink sample is called rose quartz and the dark sample is called smoky quartz. Notice how these samples do not look like crystal shapes because they have fractured. Click on image for full size ( 124K JPG) Windows to the Universe

Each type of mineral is made of a unique group of elements that are arranged in a unique pattern. However, to identify minerals you don’t need to look at the elements with sophisticated chemical tests. Since, a mineral’s unique chemical makeup determines its outward characteristics, we can identify minerals by examining their physical properties. Grab an unknown mineral and look for the properties listed below. Once you know the traits of your minerals, you can find its name by looking for minerals with those traits in a mineral identification book.

Shape
A mineral has a crystal form because of the arrangement of atoms within it. Not all crystals look the same. In fact, there are six different groups of crystal shapes. But some minerals do not look like crystals. This is typically either because the mineral sample is actually many tiny crystals that together form a large mass or because the crystal has been broken. In the former case, crystal growth is interrupted by competition for space.

Luster
Luster describes the way light is reflected by the surface of a mineral. The shiny surface of metals is described as metallic luster. Minerals that have a non-metallic luster can be described as having a glassy, pearly, or dull (earthy) luster.

Color
Most people notice the often-beautiful colors of minerals when they first look at them. Minerals can be very beautiful colors. However, if you are trying to identify a mineral, remember that the same type of mineral may be found in a variety of colors. For instance, the minerals quartz can be found in many colors including pink, purple, white or black.

Streak
Streak is the color of a mineral when it is powdered and it is often different from the color of the whole mineral. Minerals that come in different colors usually have the same color streak. To powder a little bit of a mineral, you can rub it against a small white piece of porcelain called a streak plate. You can’t measure streak with every mineral because you will only get a streak if the hardness of the mineral is less than the hardness of the plate.

Hardness
Hardness is the resistance of a mineral to abrasion. The harder a mineral is, the less likely it is to become scratched. Mohs hardness scale is a relative scale that is used to describe the hardness of minerals.

Cleavage
Minerals that have cleavage will break in a certain direction where the bonds between atoms are not strong. If you find a mineral that breaks preferentially in one direction leaving clean flat breaks, it likely has a plane of cleavage. Some minerals have several planes of cleavage in different directions.

Fracture
Minerals that do not have cleavage will fracture when broken. If the fracture has a smooth curved surface it is called a conchoidal fracture, otherwise most minerals fracture irregularly leaving a wavy uneven break.

These three crystals of the mineral quartz show how the same type of mineral can have different colors! The pink sample is called rose quartz and the dark sample is called smoky quartz. Notice how these samples do not look like crystal shapes because they have fractured. Click on image for full size ( 124K JPG) Windows to the Universe

Spotting minerals is fun! There are many different types of minerals, each with a different name and a special set of characteristics. So, if you find a mineral that you do not recognize, you can use the characteristics described below with an mineral identification book to help you figure out what its name is!

Shape
Different types of minerals have different shapes because of the special arrangement of atoms within them. Many minerals have crystal shapes. There are six different groups of crystal shapes. Some minerals do not look like crystals, either because the crystals are too small to see without a microscope or because they have been broken. When a mineral forms, the crystals start out very small but, if there is room, they can grow to be very large. Often there are so many crystals growing in the same little space that none have room to become large.

Luster
Luster is the way light is reflected by the surface of a mineral. The shiny surface of metals is called metallic luster. Other minerals have a glassy, pearly, or dull (earthy) luster.

Color
Minerals can be very beautiful colors. However, if you are trying to identify a mineral, remember that the same type of minerals can have different colors. For instance, the minerals quartz can be found in many colors including pink, purple, white, or black.

Streak
Streak is the color of a mineral when it is powdered and it is often different from the color of the whole mineral. Minerals that come in different colors usually have the same color streak. To powder a little bit of a mineral, you can rub it against a small white piece of porcelain called a streak plate. You can’t measure streak with every mineral because some are too hard to powder against the streak plate.

Hardness
The harder a mineral is, the less likely it is to be scratched. Check out Mohs hardness scale, which is used to describe the hardness of minerals.

Cleavage
Minerals that have cleavage will break in a certain direction where the bonds between atoms are not strong.

Fracture
Minerals that do not have cleavage will fracture when they are broken. If the fracture has a smooth curved surface it is called a conchoidal fracture, otherwise most minerals fracture irregularly.

These three crystals of the mineral quartz show how the same type of mineral can have different colors! Click on image for full size ( 124K JPG) Windows to the Universe

Spotting minerals is fun! There are many different types of minerals. Each has a different name and special traits. You can learn more about minerals by looking closely at them to understand their special traits. Pick up a mineral and look for the things listed below!

What shape is your mineral?
Minerals have special crystal shapes. Sometimes the crystals are too small to see or have broken apart so that the mineral does not look like a crystal shape.

What does the surface look like?
Look at what happens when light hits your mineral. The shiny surface of metals is called metallic. Other minerals have a glassy, pearly, or dull surface.

What color is your mineral?
Minerals are all different colors! Sometimes the same mineral can have many colors like quartz in the picture above.

Can you draw with your mineral?
Use your mineral like a crayon on a small white streak plate. If the mineral is soft enough, it will draw on the streak plate. Look at what color your mineral draws. Is it the same color as the mineral in your hand?

How hard is your mineral?
Some minerals are harder than others. Hard minerals are difficult to scratch. Mohs hardness scale is used to describe the hardness of minerals.

How does your mineral break?
Minerals that have cleavage will break with neat flat surfaces in places where the atoms in the mineral are only loosely connected. If your mineral does not have cleavage, it will fracture if you drop it or hit it with a hammer, making a wavy break in the crystal.