Senior High School Lesson

1. MINERALS AND ROCKS

2. •DO YOU
CONSIDER
WATER A
MINERAL?
QUESTION

3. ANSWER
• NO. IT IS NOT SOLID AND
CRYSTALLINE

4. HOW ABOUT SNOWFLAKE,
OR TUBE ICE? ARE THESE
MINERALS?

5. ANSWER
• TUBE ICE IS NOT A MINERAL, BECAUSE
IT IS NOT NATURALLY OCCURRING. BUT
A SNOWFLAKE POSSESSES ALL THE
PROPERTIES UNDER THE DEFINITION OF
A MINERAL.

6. MINERALS
•A NATURALLY OCCURRING (NOT MAN-
MADE OR MACHINE GENERATED),
INORGANIC (NOT A BYPRODUCT OF LIVING
THINGS) SOLID WITH AN ORDERLY
CRYSTALLINE STRUCTURE AND A DEFINITE
CHEMICAL COMPOSITION.
•MINERALS ARE THE BASIC BUILDING BLOCKS
OF ROCKS.

8. MINERAL NAME HALITE (TABLE SALT)
CHEMICAL COMPOSITION NaCl
LUSTER Non-metallic-vitreous; transparent to
transluscent
HARDNESS Soft (2-2.5)
COLOR White
STREAK White
CRYSTAL FORM/HABIT Cubic
CLEAVAGE Perfect cubic
SPECIFIC GRAVITY Light (2.2)
OTHER PROPERTIES Salty taste; very soluble; produces reddish
spark in flame

9. MINERAL PROPERTIES

10. LUSTER
• IT IS THE QUALITY AND INTENSITY OF
REFLECTED LIGHT EXHIBITED BY THE
MINERAL
• A. METALLIC – GENERALLY OPAQUE
AND EXHIBIT A RESPLENDENT SHINE
SIMILAR TO A POLISHED METAL.
• B. NON-METALLIC – VITREOUS
(GLASSY), ADAMANTINE
(BRILLIANT/DIAMOND-LIKE),
RESINOUS, SILKY, PEARLY, DULL

11. HARDNESS
• IT IS A MEASURE OF THE RESISTANCE OF A MINERAL (NOT
SPECIFICALLY SURFACE) TO ABRASION.

12. • HARDNESS SCALE DESIGNED BY
GERMAN
GEOLOGIST/MINERALOGIST
FRIEDRICH MOHS IN 1812 (MOHS
SCALE OF HARDNESS).

13. MOHS SCALE OF HARDNESS
• MEASURES THE SCRATCH RESISTANCE OF VARIOUS MINERALS FROM A SCALE OF
1 TO 10, BASED ON THE ABILITY OF A HARDER MATERIAL/MINERAL TO
SCRATCH A SOFTER ONE.

14. PROS OF THE MOHS SCALE
• THE TEST IS EASY.
• THE TEST CAN BE DONE ANYWHERE, ANYTIME, AS LONG AS THERE IS SUFFICIENT
LIGHT TO SEE SCRATCHES.
• THE TEST IS CONVENIENT FOR FIELD GEOLOGISTS WITH SCRATCH KITS WHO
WANT TO MAKE A ROUGH IDENTIFICATION OF MINERALS OUTSIDE THE LAB.
•

15. CONS OF THE MOHS SCALE
• THE SCALE IS QUALITATIVE, NOT QUANTITATIVE.
• THE TEST CANNOT BE USED TO ACCURATELY
TEST THE HARDNESS OF INDUSTRIAL MATERIALS

17. CRYSTAL FORM/HABIT
• THE EXTERNAL SHAPE OF A CRYSTAL OR GROUPS
OF CRYSTALS IS DISPLAYED / OBSERVED AS THESE
CRYSTALS GROW IN OPEN SPACES. THE FORM REFLECTS
THE SUPPOSEDLY INTERNAL STRUCTURE (OF ATOMS AND
IONS) OF THE CRYSTAL (MINERAL). IT IS THE NATURAL
SHAPE OF THE MINERAL BEFORE THE DEVELOPMENT OF
ANY CLEAVAGE OR FRACTURE.
• IDEAL SHAPE OF CRYSTAL FACES

19. COLOR AND STREAK
• A LOT OF MINERALS CAN EXHIBIT SAME OR SIMILAR COLORS.
• INDIVIDUAL MINERALS CAN ALSO DISPLAY A VARIETY OF COLORS RESULTING
FROM IMPURITIES AND ALSO FROM SOME GEOLOGIC PROCESSES LIKE
WEATHERING.
• B. EXAMPLES OF COLORING: QUARTZ CAN BE PINK (ROSE QUARTZ), PURPLE
(AMETHYST), ORANGE (CITRINE), WHITE (COLORLESS QUARTZ) ETC.
• C. STREAK, ON THE OTHER HAND, IS THE MINERAL’S COLOR IN POWDERED
FORM. IT IS INHERENT IN ALMOST EVERY MINERAL, AND IS A MORE DIAGNOSTIC
PROPERTY COMPARED TO COLOR. NOTE THAT THE COLOR OF A MINERAL CAN
BE DIFFERENT FROM ITS STREAK.
• D. EXAMPLES OF STREAK: PYRITE (FES2) EXHIBITS GOLD COLOR BUT HAS A
BLACK OR DARK GRAY STREAK. E. THE CRYSTAL’S FORM ALSO DEFINES THE

21. CLEAVAGE
• THE PROPERTY OF SOME MINERALS TO BREAK
ALONG SPECIFIC PLANES OF WEAKNESS TO FORM
SMOOTH, FLAT SURFACES.
• A. THESE PLANES EXIST BECAUSE THE BONDING
OF ATOMS MAKING UP THE MINERAL HAPPENS TO
BE WEAK IN THOSE AREAS.

22. • B. WHEN MINERALS BREAK EVENLY IN MORE THAN
ONE DIRECTION, CLEAVAGE IS DESCRIBED BY THE
NUMBER OF CLEAVAGE DIRECTIONS, THE
ANGLE(S) AT WHICH THEY MEET, AND THE
QUALITY OF CLEAVAGE (E.G. CLEAVAGE IN 2
DIRECTIONS AT 90°).

23. • C. CLEAVAGE IS DIFFERENT FROM HABIT; THE
TWO ARE DISTINCT, UNRELATED
PROPERTIES. ALTHOUGH BOTH ARE
DICTATED BY CRYSTAL STRUCTURE,
CRYSTAL HABIT FORMS AS THE MINERAL IS
GROWING, RELYING ON HOW THE
INDIVIDUAL ATOMS IN THE CRYSTAL COME
TOGETHER. CLEAVAGE, MEANWHILE, IS THE
WEAK PLANE THAT DEVELOPED AFTER THE

25. SPECIFIC GRAVITY
• THE RATIO OF THE DENSITY OF THE MINERAL AND THE DENSITY OF WATER
• A. THIS PARAMETER INDICATES HOW MANY TIMES MORE THE MINERAL WEIGHS
COMPARED TO AN EQUAL AMOUNT OF WATER (SG 1).
• B. FOR EXAMPLE, A BUCKET OF SILVER (SG 10) WOULD WEIGH TEN TIMES MORE
THAN A BUCKET OF WATER