Download Mineral

Mineral –a naturally occurring, inorganic, solid that has a
crystal structure and a definite chemical composition
Crystal – a solid with particles that form a repeating pattern
Streak – color of the powder of a mineral
Luster – how light reflects from a mineral
Cleavage – splitting easily along flat surfaces
Fracture – how mineral looks when broken apart in an irregular way
Fluorescence – ability to glow under ultraviolet light
Vein – narrow channel or slab of a mineral different from surrounding rock
Ore – rock that contains a metal or economically useful mineral
Smelting – melting of an ore in order extract the metal or mineral
Alloy – a mixture of two or more metals
Gemstone – hard, colorful mineral with a brilliant or glassy luster
Minerals
• more than 3,000 minerals identified
• must occur naturally in crust
• cannot come from something that was once alive
• is always a solid, with a definite volume and shape
• particles line up in a repeating pattern that is
sometimes obvious and sometimes can only be
seen under a microscope
• has a definite chemical composition, almost all are
compounds
• each has its own specific physical and chemical
properties used to identify it
Identifying Minerals
• hardness – use Mohs hardness scale which ranks 10
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minerals from softest to hardest
color – easily observed but can be used for only a few
minerals, many minerals occur in a variety of color
streak – observed by rubbing a mineral against a streak
plate, streak will not vary among samples of same
mineral
luster – another way to determine mineral as ones
containing metal will be shiny
density – each mineral has a particular density
crystal structure – crystals grow atom by atom to form a
particular structure, classified into 6 groups based on
number and angle of faces, called crystal systems
cleavage – way mineral breaks apart, if splits easily along
flat surface is said to have cleavage
fracture – if breaks into irregular shape then is said to
fracture
special properties – some glow under ultraviolet light, some
are magnetic, some radioactive, some react to acid,
some have electrical properties
Mohs Hardness Scale
Formation of minerals
• minerals used today formed several billion years ago
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formed by crystallization of melted material or through
crystallization of material dissolved in water
size of crystal depends on rate of cooling, amount of gas in magma
and chemical composition
if magma stays underground and cools slowly will develop large
crystals
if magma close to surface and cools faster has no time for large
crystals to form so will have small ones
if solution of mineral rich liquid flows into cracks and crevices in
earth will form a vein
can have the solution evaporate which will leave thick deposits of
mineral
many valuable minerals found in or near volcanic activity or
mountain building area
Lab: Determining Hardness, Color, Streak, and Luster of
a Mineral
Objective :
The purpose of this lab is to determine the hardness, streak, color and luster of various
mineral specimens.
Materials:
talc
gypsum
calcite
fluorite
feldspar
quartz
galena
hematite
pyrite
biotite or
muscovite
halite
copper penny
glass plate or microscope slide
steel nail
streak plate
magnifying glass
Safety Precautions:
Use lab aprons. Follow normal laboratory precautions.
Procedure:
1.Using your fingernail, the copper penny, glass plate and steel nail try to scratch each rock
sample. Record your observations in Data Table 1.
Rock Samples
Data Table 1
Observations
2.Complete Data Table 2 by scratching one mineral with another. If a mineral on Side
A can be scratched by a mineral on Side B place a check in the correct space. If it
cannot – leave it blank.
B Mineral Used to Scratch
Talc
Gypsum
Calcite
Talc
A - Mineral
Being
Scratched
Gypsum
Calcite
Fluorite
Feldspar
Quartz
Data Table 2
Fluorite
Feldspar
Quartz
3. Now use Data Table 1 and Data Table 2 to determine where each sample will fall on
Mohs Hardness scale. Place the samples on order from softest (1) to hardest (10) on Data
Table 3.
Mineral
Data Table 3
Hardness Number
4. Use a streak plate to determine the streak for each sample given. Place your
findings in Data Table 4.
Mineral
Data Table 4
Color of
Mineral
Color of
Streak
5.Observe the luster of each sample and place your observations in Data Table 5.
Mineral
Data Table 5
Luster
Conclusions:
1. Based on your findings which minerals were the four
hardest?
2. Which samples would you recommend a person use for a
counter or a floor in a kitchen that is being remodeled?
3. When given an unknown sample how would you go about
determining what that sample is, using the tests from this lab?