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Mineral Basics


    Minerals are the basic building blocks of rocks. Most people only know the famous or the pretty ones and don't realize the importance they have. The reason granite is so hard is because of the minerals it is composed of, or the reason marble is so soft and easily carved. Since minerals have specific structures they each have unique properties that when combined are used to identify them.

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Definition of a Mineral - A mineral is a naturally occurring, homogeneous inorganic solid substance having a definite chemical composition and characteristic crystalline structure, and hardness (dictionary.com).

Mineral Websites

Windows To The Universe Minerals.net


Mindat MEC Logo Molecule of the Month


 UC: Mineral Structure Data


Amethyst Galleries 

Identifying Minerals

Listed are the main defining characters used in identifying minerals

1. Color  

2. Hardness

3. Streak

4. Luster 


6. Specific Gravity 

7.Other (Taste, Acid Reaction, etc.)

1. Color

Color is the most useless way of identifying minerals, although it is also the principle reason people love them.


Often several minerals contain the same color

Examples of some purple minerals

Fluorite  Amethyst  Sphaerocobaltites  SugilitePurple Chalcedony



Or the same mineral has several different colors

Examples of some variations of quartz

Amethyst  Citrine  Crystal Quartz  Rose Quartz  Smoky Quartz

2. Hardness

Moh's Hardness Scale

Minerals/ Tools

Softest (Easiest to scratch)

1 - Talc 

2 - Gypsum 

2.5 - Fingernail

3 - Calcite

  3.5 - Copper Penny

4 - Fluorite

4.5 - Steel Nail

5 - Apatite

5.5 - Glass Plate

6 - Orthoclase

6 - Ceramic Tile

7 - Quartz

8 - Topaz

9 - Corundum

10 - Diamond 

Hardest (Most difficult to scratch)


3. Streak


Streak Test


Example of the color of a mineral does not effect the streak

Red Hematite     Silver Hematite

Two samples of Hematite, one silver one red. Both will give a characteristic bright red streak.

Hematite Streak

4. Luster


 - Looks like metal.

For Example - if it looks like a gold or silver ring it is probably metallic

Gold MetallicSilver Metallic



- Does not look like metal.

- Can be broken into several different categories.

- The most important category is that it is a nonmetal, the subcategories are not usually used.





Glassy (Vitreous)











5. Cleavage

 No Cleavage

Breaks into just

a random mess

Red Hematite

 Conchoidal Fracture

Shatters similar to glass with curved sharp pieces

Shattered Glass



1 direction

1 Direction Cleavage

Breaks into thin sheets


2 directions - sides @ 90°

2 Directions Cleavage at 90

Elongated box with broken ends

2 directions - sides not @ 90°

2 Directions Cleavage not at 90

Crushed box with broken ends


3 directions - sides @ 90°

3 Directions Cleavage at 90


3 directions - sides not @ 90°

3 Directions Cleavage not at 90

Crushed box

6. Specific Gravity


7. Other

There are a variety of other tests that sometimes serve as ideal identification methods for some minerals. These include:



Reaction to acid (HCl)

Reaction to Acid


Taste (salty or bitter)


Salt Halite

Mineral Halite

Striations (Parallel lines on cleavage faces)