Ch. 4 Ch. 4 Sec. 1 Properties of Sec. 1 Properties of

MineralsMinerals

Mineral or Nonmineral?Mineral or Nonmineral?mineral characteristics

rubber ball

quartz coal water diamond

Naturally occurring

NO YES YES YES YES

Inorganic YES YES NO NO YES

Solid YES YES YES NO YES

Crystal Structure

NO YES YES NO YES

Definite chemical composition

YES YES YES YES YES

Mineral or nonmineral

NON-MINERAL

MINERAL NON-MINERAL

NON-MINERAL

MINERAL

What What is a is a

mineral ?mineral ?

naturallynaturallyoccurringoccurring solidsolid crystalcrystal

structurestructureinorganicinorganicdefinitedefinite

chemicalchemicalcompositioncomposition

hardness use Mohs hardness scale

color

streak color of mineral’s powder on streak plate

luster how mineral reflects light on its surface

density mass/volume

crystal shape

cleavage mineral splits easily along flat surfaces

fracture how mineral looks when it breaks apart

special

properties

fluorescence, magnetism, radioactive,

react to acid, electrical properties

MOH’S SCALE OF HARDNESS

• 1. Talc 6. Feldspar• 2. Gypsum 7. Quartz• 3. Calcite 8. Topaz• 4. Fluorite 9. Corundum• 5. Apatite 10.  

scale that ranks minerals from softest to hardest: scale that ranks minerals from softest to hardest:

the higher the higher the number, the number, the harder the harder the mineral the mineral

Mohs Hardness ScaleMohs Hardness Scale

#1 Talc#1 Talc #2 Gypsum#2 Gypsum #3 Calcite#3 Calcite #4 Fluorite#4 Fluorite #5 Apatite#5 Apatite

#6 Feldspar#6 Feldspar #7 Quartz#7 Quartz #8 Topaz#8 Topaz #9 Corundum#9 Corundum #10 Diamond#10 Diamond

To remember the Mohs scale try remembering this To remember the Mohs scale try remembering this phrase: phrase:

TThe he GGeologist eologist CCan an FFind ind AA FFantastic antastic QQuartz, uartz, TTourists ourists CCall all DDiamond! iamond!

Tools for Testing Hardness

• You typically do not carry around a supply of the 10 minerals on the hardness scale. However, you can use the following items to help estimate the hardness of a mineral:

Finger Nail (H = 2.5) Finger Nail (H = 2.5)

Penny (H = 3) Penny (H = 3)

Knife Blade (H = 5.5) Knife Blade (H = 5.5)

Quartz ranks a 7 on Mohs hardness scale.It can scratch steel and hard glass easily.

Color is an excellent way to compare minerals—it's one of the first things that a geologist looks at.

• Minerals come in many colors—and colors are one reason that minerals are so appealing!

• Many minerals are known for their beautiful color.

Luster

Tourmanline has aTourmanline has avitreous (glassy) luster. vitreous (glassy) luster. Gold has a metallic luster.Gold has a metallic luster.

Talc has a pearly luster.Talc has a pearly luster.

MetallicMetallic

GlassyGlassy

Waxy Waxy

Greasy Greasy

PearlyPearly

DullDull

Silky Silky

Earthy Earthy

• Metallic - opaque and reflective, like metal. • Submetallic - opaque to nearly opaque and reflect well. Thin

splinters or sections of submetallic minerals are translucent. • Vitreous - reflective properties similar to glass.• Adamantine - Transparent to translucent minerals with a

high refractive index -display extraordinary brilliance and shine.• Resinous - yellow, dark orange, or brown minerals -honey

like, but not necessarily the same color.• Silky - have optical properties similar to silk cloth.• Pearly - Describes a luster similar to the inside of a mollusk

shell or shirt button. • Greasy - Luster of a mineral that appears as if it were coated

with grease.• Pitchy - tar-like appearence have a pitchy luster. • Waxy - appears as if it were coated with a layer wax.• Dull - poor reflective qualities, much like unglazed porcelain.

have a rough or porous surface.

Abhurite No cleavage Fluorite Three Cleavages

Density

Mica has a very Mica has a very low density—low density—just 2.8 just 2.8

Galena's Galena's density is 7.5 density is 7.5

Gold has one of Gold has one of the highest the highest densities—19.3! densities—19.3!

Some minerals are denser than others. That Some minerals are denser than others. That means they weigh more than other minerals of means they weigh more than other minerals of the same size. Why? Because the atoms inside the same size. Why? Because the atoms inside are heavier or packed more tightly together. are heavier or packed more tightly together. Density is also called 'specific gravity.'Density is also called 'specific gravity.'

crystal shapes

• Pyrite is called fool's gold because its brassy yellow color is very similar to gold.

• Although it looks like gold, its other physical properties are very different.

• Pyrite is harder, less dense, and more brittle. It leaves a greenish-black streak while gold leaves a golden-yellow one.

Special properties

Fluorescent minerals glow under ultraviolet light.

special properties

RadioactivityRadioactivity

• To look at radioactive minerals, you cannot see the energy being released and the damage that these minerals can cause to living organisms often until it’s too late.

• This energy can however be detected with a Geiger Counter which will show it.

Geiger CounterGeiger Counter

Grow Your Own Crystals

• To make your own salt crystals, you'll need a few items from around the house. A heat-proof, glass jar (a mason jar is excellent.)A measuring cupAbout 1 cup of boiling waterAbout 1/2 cup of saltA pencilCotton stringA spoonA paperclipA paper towel

Prepare a Supersaturated Solution• Tie the paper clip to one end of the string, and the pencil to the other end.

When you place the pencil across the top of the jar, the string should be just long enough to let the paper clip touch the bottom. Set the string, pencil, and paper clip aside.

• Boil about 1 cup of water, either in the microwave or on the stove. Pour the boiling water into the jar. Add the salt one teaspoonful at a time. Stir until each teaspoon is completely dissolved. You may be tempted to add all the salt at once, but the experiment won't work as well if you do. Be patient. Eventually, you'll find a small amount of salt will not dissolve and collects at the bottom of the jar. You have reached supersaturation. Once the solution is supersaturated, stop adding salt.

• Next, you'll put it all together -- and find out what to do with that string and the paper towel.

Put It All Together • Lower the paper clip and string into the water and rest

the pencil across the top of the jar. Cover the jar lightly with a paper towel. This will keep dust out of the jar. Place the jar where it won't be disturbed for a couple of days.

• Table salt (halite) crystals form as cubes. After about 12 hours, you should be able to see small crystals forming at the bottom of the jar, on the paper clip, and along the string. Some may even form on the surface of the water, like a wreath around the string. After 24 hours, you should see definite crystal forms.

• After all this work, let's see the results and how to find out more about minerals.

Results and Resources • After one or two days, you'll be able to see cubes of salt

crystals. Some may form alone and grow larger, while others may form clusters.

• If you'd like to experiment with another mineral that has a completely different shape, try using 1 and 1/2 cups of Epsom salts (magnesium sulfate) instead of 1/2 cup of salt. The Epsom salt crystals will tend to form on the bottom of the jar and are generally shaped like stubby prisms.

Properties of minerals Name of Mineral Color of mineral Color of

streakLuster

Activity-Finding the Density of Minerals

Amethyst Citrine Malachite Snowflake Obsidian

Hematite

Mass of mineral (g)

Volume of water without mineral

(mL)

Volume of water with mineral (mL)

Volume of water displaced (mL)

Volume of water displaced (cm3)

Density (g/cm3)

Activity-Finding the Density of Minerals

Pyrite Quartz Hematite

Mass of mineral (g) 15 g 80 g 150 gVolume of water

without mineral (mL)100 mL 100 mL 100 mL

Volume of water with mineral (mL)

105 mL 130 mL 129 mL

Volume of water displaced (mL)

5 mL 30 mL 29 mL

Volume of water displaced (cm3)

5 cm3 30 cm3 29 cm3

Density (g/cm3) 3 g/cm3 2.67 g/cm3 5.17 g/cm3

A Mouthful of MineralsToothpaste Minerals Present Predictions Observations

Colgate

Gleem

Ultra-Brite

Problem: What effect do the minerals in toothpaste have on the toothpaste’s ability to clean?

A Mouthful of MineralsToothpaste Minerals Present Predictions Observations

Colgate Silica, sodium bicarbonate, sodium flouride, calcium, titanium dioxide

Gleem Sodium flouride, silica, titanium

dioxide, sodium phosphate

Ultra-Brite Sodium flouride, silica, tetrasodium pyrophosphate, titanium dioxide

Problem: What effect do the minerals in toothpaste have on the toothpaste’s ability to clean?