2. Turn to the lab manual-
• DIAGNOSITIC VS AMBIGUOUS
• LUSTER
• STREAK
• CRYSTAL HABIT
• BREAKAGE
• SPECIFIC GRAVITY
3. YOU WILL USE TABLE ONE
• On page 14
• Specimen number (1-24)
• Luster-for example-”metallic”
• Color-for example-”dark grey”
• Hardness-for example-”less than a finger nail”
• breakage_-exhibits cleavage In one direction
• Other diagnositcs-
4. Do this 24 times
Specimen
number
Luster Color Hardness breakage Other
diagnositcs-
5. • Hardness
• Lustre and diaphaneity
• Colour and streak
• Cleavage, parting, fracture, and tenacity
11. Hardness
• The hardness of a mineral defines how much
it can resist scratching. This physical property
is controlled by the chemical composition and
crystalline structure of a mineral
12. • A mineral's hardness is not necessarily
constant for all sides, which is a function of its
structure; crystallographic weakness renders
some directions softer than others.
13. • An example of this property exists in kyanite,
which has a Mohs hardness of 5½ parallel to
[001] but 7 parallel to [100].[60]
14. • The most common scale of measurement is
the ordinal Mohs hardness scale. Defined by
ten indicators, a mineral with a higher index
scratches those below it.
15. Mohs hardness scale
Mohs hardness Mineral Chemical formula
1 Talc Mg3Si4O10(OH)2
2 Gypsum CaSO4·2H2O
3 Calcite CaCO3
4 Fluorite CaF2
5 Apatite Ca5(PO4)3(OH,Cl,F)
6 Orthoclase KAlSi3O8
7 Quartz SiO2
8 Topaz Al2SiO4(OH,F)2
9 Corundum Al2O3
10 Diamond C
17. • Lustre indicates how light reflects from the
mineral's surface, with regards to its quality
and intensity. There are numerous qualitative
terms used to describe this property, which
are split into metallic and non-metallic
categories
18. • Metallic and sub-metallic minerals have high
reflectivity like metal; examples of minerals
with this lustre are galena and pyrite
20. Colour and streak
• Colour is typically not a diagnostic property of
minerals. Shown are green uvarovite (left) and
red-pink grossular (right), both garnets. The
diagnostic features would include
dodecahedral crystals, resinous lustre, and
hardness around 7.
21. streak
• The streak of a mineral refers to the colour of
a mineral in powdered form, which may or
may not be identical to its body colour.[66] The
most common way of testing this property is
done with a streak plate, which is made out of
porcelain and coloured either white or black.
The streak of a mineral is independent of trace
elements[62] or any weathering surface.[66]
22. streak
• A common example of this property is
illustrated with hematite, which is coloured
black, silver, or red in hand sample, but has a
cherry-red to reddish-brown streak. Streak is
more often distinctive for metallic minerals, in
contrast to non-metallic minerals
23. streak
• Streak testing is constrained by the hardness
of the mineral, as those harder than 7 powder
the streak plate instead
25. Cleavage
• Perfect basal cleavage as seen in biotite
(black), and good cleavage seen in the matrix
(pink orthoclase).
26. atomic arrangement
• By definition, minerals have a characteristic
atomic arrangement. Weakness in this
crystalline structure causes planes of
weakness, and the breakage of a mineral
along such planes is termed cleavage.
27. "perfect", "good", "distinct", and
"poor".
• The quality of cleavage can be described
based on how cleanly and easily the mineral
breaks; common descriptors, in order of
decreasing quality, are "perfect", "good",
"distinct", and "poor". In particularly
transparent mineral, or in thin-section,
cleavage can be seen a series of parallel lines
marking the planar surfaces when viewed at a
side.
28. quartz does not have a crystallographic
traits
• . Cleavage is not a universal property among
minerals; for example, quartz, consisting of
extensively interconnected silica tetrahedra,
does not have a crystallographic weakness
which would allow it to cleave. In contrast,
micas, which have perfect basal cleavage,
consist of sheets of silica tetrahedra which are
very weakly held together.
29. function of crystallography
• As cleavage is a function of crystallography,
there are a variety of cleavage types. Cleavage
occurs typically in either one, two, three, four,
or six directions. Basal cleavage in one
direction is a distinctive property of the micas.
Two-directional cleavage is described as
prismatic, and occurs in minerals such as the
amphiboles and pyroxenes.
30. cubic (or isometric) cleavage
• Minerals such as galena or halite have cubic
(or isometric) cleavage in three directions, at
90°; when three directions of cleavage are
present, but not at 90°, such as in calcite or
rhodochrosite, it is termed rhombohedral
cleavage. Octahedral cleavage (four directions)
is present in fluorite and diamond, and
sphalerite has six-directional dodecahedral
cleavag
31. Tenacity
• Tenacity is related to both cleavage and
fracture. Whereas fracture and cleavage
describes the surfaces that are created when a
mineral is broken, tenacity describes how
resistant a mineral is to such breaking.
Minerals can be described as brittle, ductile,
malleable, sectile, flexible, or elastic.[73]
32. Go into groups-finish this lab today
• First exam in one this material
• Will email the power point to you now
