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• DIAGNOSITIC VS AMBIGUOUS• LUSTER• STREAK• CRYSTAL HABIT• BREAKAGE• SPECIFIC GRAVITY

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-

Do this 24 timesSpecimen number

Luster Color Hardness breakage Other diagnositcs-

• Hardness• Lustre and diaphaneity• Colour and streak• Cleavage, parting, fracture, and tenacity

Hardness

Lustre and diaphaneity

Colour and streak

Cleavage, parting, fracture, and tenacity

lastly

• Specific gravity• Tenacity• Rxn with HCl• Magnetic• Feel (not taste)

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

• 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.

• An example of this property exists in kyanite, which has a Mohs hardness of 5½ parallel to [001] but 7 parallel to [100].[60]

• 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.

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

Lustre and diaphaneity

• Pyrite has a metallic lustre• .

• 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

• Metallic and sub-metallic minerals have high reflectivity like metal; examples of minerals with this lustre are galena and pyrite

Colour and streak

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.

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]

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

streak

• Streak testing is constrained by the hardness of the mineral, as those harder than 7 powder the streak plate instead

Cleavagebiotite (black), (pink orthoclase).

Cleavage

• Perfect basal cleavage as seen in biotite (black), and good cleavage seen in the matrix (pink orthoclase).

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.

"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.

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.

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.

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

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]

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lastly

• Specific gravity• Tenacity• Rxn with HCl• Magnetic• Feel (not taste)