1. COLOR
Color is not usually a definitive property of a mineral. Color will only be definitive is it is a major constituent in the mineral.
A good example of this is malachite which is green from the Cu.
However most minerals have a variety of colors.
The mineral sphalerite can be yellow, black, red, green or varieties thereof.
Quartz is usually colorless, however it can have many colors depending on trace amounts of cations that substitute in the structure.

2. Some Colors of Quartz

3. STREAK
For opaque minerals, if you rub the sample across a streak plate, it will leave a colored powder. This streak is distinctive for minerals and is used to identify minerals.
Hematite can be brown, black, metallic gray and earthy but in all cases it gives a red-brown streak.

4. Varieties of Hematite

5. Play of Colors: Iridescence
For example, plagioclase, variety labradorite
Interference of light either at the surface or in the interior of a mineral--series of color--much the same as oil on water. Opal is another example.

6. Plagioclase-variety Labradorite

7. LUSTER Metallic or non-metallic
Non-metallic: vitreous or glassy; silky; resinous; pearly; greasy; waxy, dull; earthy

8. Examples of metallic luster

9. Example of non-metallic luster
Vitreous--quartz

10. Example of non-metallic luster
Silky--example satinspar

11. Example of non-metallic luster
Resinous--sphalerite

12. Example of non-metallic luster
Pearly--Talc

13. Example of non-metallic luster
Dull--Kaolinite

14. Example of non-metallic luster
Earthy--Goethite (limonite)

15. Example of non-metallic luster
Waxy--serpentine

16. LUMINESCENCE
The emission of light not due to incandescence. For example, fluorescent minerals colors under ultraviolet light. Minerals include varieties of calcite, fluorite and scheelite.

17. The fluorite on your left is fluorescing
The fluorite on your right is the correct color

18. Hardness
The resistance a mineral has to being scratched. It is measured on a qualitative scale called the Mohs’ Hardness scale.

19. Cleavage
The Tendency of a mineral to split along planes parallel to the crystal faces, leaving smooth flat surfaces in one or more directions

20. If a mineral doesn’t have cleavage it will have fracture
If a mineral doesn’t have cleavage it will have fracture. That is it will not break with flat even surfaces. There are many types of fracture.
Fracture

21. Fracture continued
Some adjectives used to describe fracture are: hackly = very jagged
even = smooth but not flat
uneven = rough & irregular but
not sharp or jagged
conchoidal = broken glass look

22. Acid Test
A weak solution of HCl is placed on a mineral to see if it reacts. The reaction is would be a fizzing or bubbling on the surface of the mineral. That means the mineral is a carbonate, likely a limestone or calcite

23. Other Properties Some other mineral properties: Taste Specific gravity
Smell
flexibility

24. Identification
No one mineral property by itself can be trusted to identify the mineral. It is the combination of mineral properties that are used for identification.