Rocks and Minerals A mineral is a naturally occurring inorganic compound with a unique chemical structure and physical properties. A rock is a solid, stony mass composed of a combination of minerals or other organic compounds. For example, quartz and feldspars are minerals, but when formed together, they make a rock, granite”  To determine if an Earth rock is a mineral, it should exhibit the following characteristics Naturally occurring  Inorganic  Can be represented by a chemical formula Crystalline structure Solid Most minerals form by inorganic processes but some, identical in all respects to inorganically formed minerals, are produced by organic processes Transparency describes how well light passes through a mineral sample There are three degrees of transparency: transparent, translucent, and opaque. Habit of a mineral may be define as the size and shape of the crystal, and the structure of form shown by the crystal. 1. Accicular minerals showing needle like crystal. E.g. natrolite 2. Fibrous minerals showing an aggregate of long thin fibers. E.g. Asbestos 3. Tabular minerals showing bladed habit occur as small knife blades. E.g. Kyanite 4. Granular minerals which occur as aggregate of equidimensional grains. E.g. chromites 5. Pisolitic minerals which occur as aggregate of rounded grains of a pea size. E.g. oolite 6. Columnar minerals showing columnar crystal. E.g. tourmaline Minerals strength determines how easy the mineral breaks or deforms when exposed to stress. Reaction with Acid. Some minerals, especially carbonate minerals, react visibly with acid. (Usually, a dilute hydrochloric acid [HCl] is used.) When a drop of dilute hydrochloric acid is placed on calcite, it readily bubbles or effervesces, releasing carbon dioxide

1. Rocks and Minerals

2. A mineral is a naturally
occurring inorganic
compound with a unique
chemical structure and
physical properties.

3. A rock is a solid, stony
mass composed of a
combination of minerals or
other organic compounds.

4. For example, quartz and
feldspars are minerals, but
when formed together,
they make a rock, granite”

5. To determine if an Earth
rock is a mineral, it should
exhibit the following
characteristics

6. Naturally occurring

9. Inorganic

10. Can be represented by a
chemical formula

13. Crystalline structure

15. Solid

16. Most minerals form by
inorganic processes but
some, identical in all
respects to inorganically
formed minerals, are
produced by organic

17. Physical Properties
of Minerals

18. Luster describes the
appearance of a mineral
when light is reflected from
its surface.

19. Metallic, having the look of
a polished metal

22. Submetallic, having the
look of a metal that is dulled
by weathering or corrosion

24. Non-metallic, not looking
like a metal at all.

26. Transparency describes
how well light passes
through a mineral sample

27. There are three degrees
of transparency:
transparent, translucent,
and opaque.

31. Color is one of the most
obvious properties of a
mineral but it is often of
limited diagnostic value,
especially in minerals that
are not opaque.

32. Quartz, for example, can
vary from colorless to
white to yellow to gray to
pink to purple to black.

34. Never use color as a final
diagnostic property --
check other properties
before making an
identification.

35. Streak refers to the color of
the mineral in its powdered
form, which may or may not
be the same color as the
mineral.

36. Streak is obtained by
scratching the mineral on
an unpolished piece of
white porcelain called a
streak plate

37. Streak is commonly more
reliable than color for
identification.

38. The streak of this dark gray
mineral (hematite), obtained
by rubbing it on the white
streak plate is reddish
brown.

39. A mineral that exhibits
cleavage consistently
breaks, or cleaves, along
parallel flat surfaces called
cleavage planes.

40. A mineral fractures if it
breaks along random,
irregular surfaces. Some
minerals break only by
fracturing, while others both
cleave and fracture.

42. Habit of a mineral may be
define as the size and
shape of the crystal, and
the structure of form
shown by the crystal.

43. 1. Accicular minerals
showing needle like
crystal. E.g. natrolite

45. 2. Fibrous minerals
showing an aggregate of
long thin fibers. E.g.
Asbestos

48. 3. Tabular minerals
showing bladed habit
occur as small knife
blades. E.g. Kyanite

50. 4. Granular minerals
which occur as aggregate
of equidimensional grains.
E.g. chromites

52. 5. Pisolitic minerals which
occur as aggregate of
rounded grains of a pea
size. E.g. oolite

54. 6. Columnar minerals
showing columnar crystal.
E.g. tourmaline

56. Minerals strength
determines how easy the
mineral breaks or deforms
when exposed to stress.

57. Hardness is the resistance
of a mineral to scratching or
abrasion by other materials.

58. Hardness is determined by
scratching the surface of
the sample with another
mineral or material of
known hardness.

59. The standard hardness
scale, called Mohs
Hardness Scale consists of
ten minerals ranked in
ascending order and 10 is
considered as the hardest.

61. The property of tenacity
describes the behavior of
a mineral under
deformation.

62. It describes the physical
reaction of a mineral to
externally applied stresses
such as crushing, cutting,
bending, and striking
forces.

63. Adjectives used to
characterize various types of
mineral tenacity include
'brittle,' ‘sectile,' 'flexible,'
'elastic,' 'malleable,' and
'ductile,’

64. Brittle breaks or powders
easily.
Malleable can be hammered
into thin sheets.
Sectile can be cut into thin
shavings with a knife.

66. Sectile
orpiment

67. Ductile bends easily and
does not return to its original
shape.
Flexible bends somewhat
and does not return to its
original shape.
Ductile bends easily and
does not return to its original
shape.
Flexible bends somewhat
and does not return to its
original shape.

68. Ductile
copper

69. Flexible
gypsum

70. Elastic bends but does
return to its original shape.

71. Elastic
mica

72. Additional Properties

73. To test a mineral for
magnetism, just put the
magnet and mineral together
and see if they are attracted.

76. Reaction with Acid.
Some minerals, especially
carbonate minerals, react
visibly with acid. (Usually, a
dilute hydrochloric acid [HCl]
is used.)

77. Taste, Odor, Feel
Some minerals have a
distinctive taste, some a
distinctive odor, and some a
distinctive feel