Berg, Director E. Peabody Champaign, IL info isgs. All rights reserved. For permissions information, contact the Illinois State Geological Survey. Terms of use Privacy Statement. Skip to main content. Using Characteristics of Minerals to Identify Them. Hardness The ability to resist being scratched—or hardness—is one of the most useful properties for identifying minerals.
Approximate Hardness Item 1 Blackboard Chalk 2. Tape the edges of the glass with duct tape. You may be able to get this cut at a local hardware store.
Try to find an old, broken or worn flat file Luster Luster is how a mineral reflects light. Streak Streak is the color of the powdered mineral, which is usually more useful for identification than the color of the whole mineral sample. Specific Gravity Specific gravity is the ratio between the mass weight of a mineral and the mass weight of an equal volume of water.
Search form Search. Window glass 2 inches square; use caution making this scratch plate. To demonstrate how to use the scale, understand the following example: Suppose a mineral scratches Fluorite , but not Apatite , then it has a hardness between 4 and 5. There are various hardness testing kits. One type consists of 10 metal rods, each one containing a fragment of one of the minerals in the Moh's scale.
Another type consists of large, low cost specimens of the Moh's minerals, labeled and stored in a wooden compartment box. The Diamond is either absent or a chip attached to a small metal rod.
The Diamond is really unnecessary, since no minerals are between hardness 9 and A mineral is struck with a metal rod or "testing mineral" to test its hardness. It is tested in the manner of the following example:. Two minerals with equal hardness will scratch each other. This gives an advantage to the hardness testing kit that includes real minerals over rods. One can scratch the mineral from the kit instead of scratching a nice specimen. In addition, one can also get more exact results by seeing if both minerals scratch each other.
Minerals can be damaged and lose value if not scratched properly. If a mineral testing kit is composed of minerals as opposed to rods , it is preferable for the testing kit mineral to be scratched over the specimen. If this cannot be done, than the specimen has to be scratched.
This should be done in an area where a scratch will be less noticeable, since it will make a permanent mark. Hardness can be easily detected without a "kit". All one needs to know is the hardness of certain items including the ones mentioned above and minerals in his collection. Breaking a mineral breaks its chemical bonds. Since some bonds are weaker than other bonds, each type of mineral is likely to break where the bonds between the atoms are weaker.
For that reason, minerals break apart in characteristic ways. Cleavage is the tendency of a mineral to break along certain planes to make smooth surfaces. Halite breaks between layers of sodium and chlorine to form cubes with smooth surfaces Figure below. One reason gemstones are beautiful is that the cleavage planes make an attractive crystal shape with smooth faces.
Fracture is a break in a mineral that is not along a cleavage plane. Fracture is not always the same in the same mineral because fracture is not determined by the structure of the mineral. Minerals may have characteristic fractures Figure below. Metals usually fracture into jagged edges. If a mineral splinters like wood, it may be fibrous. Some minerals, such as quartz, form smooth curved surfaces when they fracture.
Some minerals have other unique properties, some of which are listed in Table below. Hint: It is most likely found on your dinner table. Skip to main content. Search for:. Mineral Identification Lesson Objectives Explain how minerals are identified. Describe how color, luster, and streak are used to identify minerals. Explain how the hardness of a mineral is measured.
Identify additional properties that can be used to identify some minerals. Vocabulary cleavage fracture hardness luster mineralogist streak Introduction Minerals can be identified by their physical characteristics.
How are Minerals Identified?
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