Transcript WHAT IS ROCK? - GemKids

GIA JUNIOR GEMOLOGIST PROGRAM™
Boy Scouts of America
Merit Badge Series: Geology
GEOLOGY AND GEMS
Geology is the science and study of the Earth,
its composition, structure, physical properties,
history, and the processes that shape it.
WHAT IS ROCK?
• A rock is a solid material made up of minerals
• Rocks are the building blocks that make up the earth
• Rocks tell a story about the earth and how it was formed
IGNEOUS ROCK
Eruption of Mount St. Helens volcano,1980
Pumice
Igneous rocks start out in a molten or semi-molten state and
become solid when they cool.
IGNEOUS ROCK FORMATION
extrusive
intrusive
IGNEOUS ROCKS
Granite
Lava
SEDIMENTARY ROCK
Sandstone
Sedimentary rocks are formed by layers of sediments squeezed
and pressed together over a long period of time.
METAMORPHIC ROCK
CONVICT LAKE, CALIFORNIA
Slate
Metamorphic rocks have their makeup,
texture, or structure changed by great
heat, pressure, or both.
METAMORPHIC
MOUNT CHO OYU, NEPAL (26,906 ft.)
Marble with spinel
DEFORMATION OF ROCKS
• Rocks are continually being subjected
to forces that bend them.
• A fold can be defined as a bend in rock
that is the response to compressional
forces.
• Folds are most visible in rocks that
contain layering.
ROCK ACTIVITY
CAREERS IN GEOLOGY
• What is someone called who studies
geology?
 A geologist
• What does a geologist do?
 They work to understand the
history of our planet so that they
can foresee how past events
might influence the future.
ADVANCED CAREERS IN GEOLOGY
MINERALOGY
Mineralogy is the science that involves the
chemistry, crystal structure, and physical
(including optical) properties of minerals and
the processes that create them.
MINERALS
To be considered a mineral a material must
have all of the following features:
• Solid
• Inorganic
• Formed in Nature
• Specific Chemical Composition
• Crystal Structure
IDENTIFICATION OF MINERALS
CRYSTAL STRUCTURE
CRYSTAL STRUCTURE
The most exciting aspects of minerals are
their beautiful and elegant crystal forms.
A mineral’s crystal form is an exterior
expression of what is happening on the
inside of a mineral at the atomic level.
CRYSTAL STRUCTURE
ACTIVITY
Harder
MOHS HARDNESS SCALE
Softer
140x
124,000x
10 9 8 7 6 5 4 3 2 1
10.
9.
8.
7.
6.
5.
4.
3.
2.
1.
Diamond
Corundum (Sapphire/Ruby)
Topaz
Quartz
Orthoclase feldspar
Apatite
Fluorite
Calcite
Gypsum
Talc
IDENTIFICATION OF MINERALS
HOW DO MINERALS GET THEIR COLOR?
• What color is sunlight/white light?
 All the colors in a rainbow
• When light hits an object, some of the
colors get absorbed
• Other colors reflect within the object and
transmit back to our eyes
• This is the color we see
COLOR ACTIVITY
IDENTIFICATION OF MINERALS
STREAK
• Streak testing is a method used in
mineral identification
• Helps distinguish gold (yellow
streak) from pyrite (black streak)
• Streak testing is destructive and not
recommended
IDENTIFICATION OF MINERALS
LUSTER
Luster is a way that light interacts with the surface of a
material
• High-luster Categories
 Adamantine - diamond like
 Metallic
• Medium-luster Categories
 Vitreous - glass like
• Low-luster Categories
 Waxy – Dim and blurred like the surface of a
candle
LUSTER ACTIVITY
GEMOLOGY
Gemology is the science,
art and profession of
identifying and evaluating
gemstones. It may be
considered a branch of
mineralogy.
WHAT IS A GEM?
Beautiful
Rare
Durable
GEMSTONE FAMILIES
Group
• A family of gems from several closely
related mineral species
Species
• A broad gem category based on
chemical composition and crystal
structure
Variety
• A subcategory of species, based on
color, transparency, or phenomena (an
optical effect, like a star in star sapphire,
or the blue sheen in moonstone)
INCLUSIONS
Inclusions can be a variety of objects
enclosed within a gemstone or those
that extend into it from the surface.
Inclusions can be:
• Other minerals
“Lily-pad” inclusion in a peridot
• Gas
• Liquid
Three-phase inclusion in an
emerald
INCLUSIONS IN ORGANIC MATERIAL
Inclusions can also be
found in organic material:
• Leaves
• Bugs such as termites,
mosquitoes, or ants
• Tree bark
PHENOMENA
Some gems display special effects when they
interact with light. These stones are called
phenomenal gems because they display
unusual optical effects.
INCLUSION ACTIVITY
CAREERS IN GEMOLOGY
COMMERCIAL USES FOR ROCKS
AND MINERALS
USES FOR IGNEOUS ROCKS
USES FOR SEDIMENTARY ROCKS
USES FOR METAMORPHIC ROCKS
INDUSTRIAL AND COMMERCIAL MINERAL
USE
INDUSTRIAL AND COMMERCIAL MINERAL
USE
Photo credits:
Joel Beeson
Richard D. Fisher
Chuck Fryer
Tino Hammid,
Gary Hill
Tory Kooyman
Pacific Studios, Newport, Oregon
Valerie Power
Maha Tannous
Parke D. Snavely, Jr. of the USGS
Eric Welch
Robert Weldon