laboratory 2 Flashcards
(22 cards)
How can igneous rocks be classified?
Beyond this, IGNEOUS ROCKS can also be classified
according to SiO2 (SILICA) content.
Generally speaking, SiO2 (SILICA) is most important
component in IGNEOUS ROCK.
SiO2 (SILICA) accounts for nearly HALF OR MORE of the
mass/weight of IGNEOUS ROCK.
MAGMA (and LAVA) from STRATOVOLCANOES is:
➢ very VISCOUS (STICKY)
➢ RICH IN SILICA!
MAGMA (and LAVA) from SHIELD VOLCANOES is:
➢ rich in IRON and MAGNESIUM
➢ does not contain much silica
➢ less STICKY
Igneous rocks can be classified according to magma/lava
MAGMA/LAVA can be classified as FELSIC or
MAFIC depending on SILICA (SiO2) content.
Which stratovolcano caused a year without summer?
Mount Tambora, Indonesia due to volcanic airborne material in atmosphere blocking sunlight
What is felsic magma/lava?
➢ higher VISCOSITY (stickier)
➢ less IRON (Fe)
➢ richer in SILICA (SiO2)
➢ found near SUBDUCTION ZONES
What is mafic magma/lava?
➢ lower VISCOSITY (less sticky)
➢ richer in IRON (Fe)
➢ less SILICA (SiO2)
➢ found at HOT SPOTS and mid-oceanic ridges
Felsic igneous rock
GREATER THAN 65% SILICA
include rhyolite and granite
intermediate igneous rock
55 – 65% SILICA
include andesite and diorite
mafic igneous rock
45 – 55% SILICA
include basalt and gabbro
ultramafic igneous rock
LESS THAN 45% SILICA
include peridotite
EXTRUSIVE IGNEOUS rocks have INTRUSIVE equivalents and visa versa.
Whereas process by which they form, and appearance differs, their content/composition is very comparable.
BASALT is EXTRUSIVE equivalent of INTRUSIVE GABBRO.
ANDESITE is EXTRUSIVE equivalent of INTRUSIVE DIORITE.
RHYOLITE is EXTRUSIVE equivalent of INTRUSIVE GRANITE.
note: intrusive examples typically lighter than
extrusive equivalents!
Sulfur
➢ an ELEMENT (16 protons) and a MINERAL
➢ has a distinctive YELLOW colour and odour
➢ melts at a low temperature (108oC)
➢ it has a low density (approximately 2 grams/cubic
centimeter or 2 grams/milliliter) and therefore
feels “light”
How many minerals on earth?
Over 4000 naturally occurring minerals on Earth
When do minerals from?
➢ magma cools
➢ water rich in molecules that make-up MINERALS
evaporates, allowing the molecules to
CRYSTALLIZE (this is what occurs in underground
caves; see image).
What mineral crystals can be?
➢ SMALL if form in confined spaces (e.g., between other solids/other MINERALS)
➢ LARGE if given necessary time and space (e.g., within GEODES).
What is a stalagmite and stalactite and what can they contain?
STALAGMITE: upward growing mound of
MINERAL deposits (often CaCO3) that originated in water that dripped onto cave floor.
STALACTITE: icicle-shaped formations/MINERAL deposits that hang from ceiling of a cave.
may contain other materials such as lava and even AMBERAT which is CRYSTALLIZED pack rat urine!
What are geodes?
hollow rock formations with minerals, often
QUARTZ CRYSTALS (SiO2) that have developed
inside.
How do geodes form?
➢ material around a hollow in the ground (e.g., animal
burrow) turns to rock
➢ gas bubbles/pockets are found inside IGNEOUS
rock/when lava cools around gas bubbles/pockets
Pockets in GEODES allow for water to seep in.
Over time, water evaporates, leaving behind molecules
that make up MINERALS. Molecules CRYSTALLIZE,
forming MINERAL CRYSTALS.
CRYSTALS within pocket can form over
thousands/millions of years, with largest CRYSTALS
typically being oldest.
What gives minerals different colours even though they are the same mineral?
Presence of additional ELEMENTS/IMPURITIES in MINERAL CRYSTALS can give them variety of colours.
What impurities turns which color?
-if IRON (Fe) present, MINERAL CRYSTAL turns RED or PURPLE
-if TITANIUM (Ti) present, MINERAL CRYSTAL turns BLUE
-if NICKEL (Ni) or CHROMIUM (Cr) present, MINERAL CRYSTAL turns GREEN
-if MANGANESE (Mn) present, MINERAL CRYSTAL turns PINK
How many different mineral classes are according to chemical composition?
78
Dana classification system
9 main mineral classes: native elements, sulfides (S2-), sulfates (SO42-), halides (Cl- or F-), oxides (O or O2-), carbonates (CO32-), phosphates (PO43-), silicates (silicon+oxygen)
Are organics true minerals?
ORGANICS: NOT TRUE MINERALS
This last class accounts for materials such as AMBER,
which comes from trees and AMBERAT, which comes
from pack rats.
They are not TRUE minerals since they are ORGANIC.
ORGANIC MINERALS contain CARBON (C), more
specifically CARBON-HYDROGEN bonds and may come
from previously living beings.
