3-1 What is a mineral?3-2 Identifying minerals?
(epsomite)
{enrich} What is a Mineral? More than 4,000 minerals (40-50 new minerals
identified each year!) but only 100 common minerals about 20 minerals make up most of Earth’s crust native elements occur in nature in pure form (ex:
gold, copper, diamond, sulfur, graphite, silver, and platinum)
Most minerals are COMPOUNDS… (a chemical combination of two or more elements), while rocks are mixtures of minerals (and sometimes organic matter like shells)
Some minerals are elements (like copper, gold and diamonds)
{enrich} Classification of minerals
95% of the earth’s crust is made of silicates (minerals made of silicon and oxygen): ex: quartz SiO2)
sulfide (+ sulfur) ex: cinnabar (HgS)
sulfate (+sulfur & O)
carbonate (C & O) ex: calcite: CaCO3
oxide (+oxygen) ex: corundum: Al2O3
halide –ex: salt
Characteristics of ALL minerals: (INSCC)--foldable--
Inorganic Natural Solid Compound (or
element) Crystal system
Inorganic– never alive– not from
something alive– rocks can have
organic matter
Naturally occurring– not synthetic or
artificial or man-made
Solid– at room temperature
Chemical composition– some single element
in pure form (native elements) like copper, diamond, sulfur
– most are compounds like quartz (SiO2) and cinnabar (HgS)
– rocks are mixtures– Can you read a
chemical equation?
Crystal system– repeating pattern
with flat sides (called faces)
– most are only visible with a microscope
8 ways to test the identify of a mineral
1--hardness 2--color 3--streak color 4--luster
5--density 6--crystal structure 7--cleavage/fracture 8--special properties
Hardness how easy is it to scratch the mineral? Moh’s scale
– 1812 by Friedrich Mohs– 1 (talc) - 10 scale (diamond)– common substances:
fingernail=2.5 penny=3-3.5 glass=5.5-6 steel=5-5.5 streak plate=
6.5-7.5
Colors of QUARTZ
Two colors
Color– easy but not reliable– color may change over
time– some minerals have
MANY colors (like quartz)--due to impurities
– many minerals have the same color
Streak Color--practice– more reliable than
regular color– color of its powder– use streak plate
(unglazed tile)– examples:
pyrite=black gold=golden, yellow
Luster– how a mineral
reflects light from its surface
– 1. metallic (shiny)– 2. nonmetallic:
glassy, dull, earthy, waxy, pearly
Density– mass/volume– remains the same (no
matter the specimen size)
– also called “heft”– may use “specific
gravity” (same as density, but no units)
Types of luster
Crystal System– Example: cubic-– Example:
hexagonal
Cleavage/Fracture (paper towel demo)– how a mineral BREAKS – 1. Cleavage=smooth break– 2. Fracture=irregular break—
rough, jagged, or curved (most minerals have fracture) quartz=curved, shell-like surface copper and iron=hacky fracture
(forms jagged points)
Special Properties
Fluorescence (glow under UV light)--scheelite
magnetic--magnitite radioactive--uraninite fizzes (gives off CO2)
in acid– calcite (demo)
Very malleable (easy to shape)--gold
earthy odor--clay soapy feeling--talc feels greasy--graphite double refraction--
optical calcite
Special Properties:
A rock is a mixture of _____________. minerals
Mystery mineral game:
Pick a mineral from pp. 800-801 other classmates must ask yes/no questions
to determine the identity of the mystery mineral (like “20 Questions)
LAB: What mineral do you have?
Find color and streak color What is the luster? Find the hardness (a range) Find density (use water displacement for volume)
—could use “heft” AFTER 2-4 tests are completed, try to identify
the mineral, then... Bring the mineral to Mrs. McMullan when
finished to see if you are correct and to get another mineral to identify.
Questions for review Which of the following definitions best describes
a MINERAL?– a. a substance that cannot be separated or
broken down into simpler substances by chemical reactions
– b. a substance made up of atoms of two or more different elements joined by chemical bonds
– c. a naturally formed inorganic solid that has a definite crystalline structure
– d. a solid whose atoms, ions, or molecules are arranged in a definite pattern
Minerals that contain one or more elements combined with silicon and oxygen are called _________ {enrich}
silicates Which mineral can be identified by tasting? halite (salt) What is the difference between a mineral and
a rock? Minerals are elements or compounds. Rocks are mixtures (or minerals).