Answers to questions for Basic building
blocks of rocks - from atoms to minerals.
What controls how
different atoms/ions combine together?
- ionic charge and type of bonding.
- covalent bonds
- ionic bonds
- metallic bonds
- van der Waals
- ionic size: function of elemental species
and electron configuration.
What are isotopes and why they are important?
It is the number of protrons in the nucleus
that determines what element an atom is. The number of neutrons
can vary. Isotopes are different versions of an element with different
atomic weights due to more or less neutrons than other versions.
Isotopes can be either stable or unstable. The latter produce
radioactivity as they decay. Hydrogen as the isotopes deuterium
and tritium, with one and two neutrons respectively. Both are
unstable, and are what makes 'heavy water.'The amount and ratios
of isotopes in geologic material can be very informative.
What
are diagnostic properties for hand specimen identification?
- cleavage: reflects
fundamental atomic architecture
- crystal form: reflects
fundamental atomic architecture.
- color: can reflect
either trace impurities, or fundamental composition/architecture.
- luster: affected by
weathering patina, lighting conditions.
- density: relects fundamental
composition/architecture.
- association: reflects
origin, often an overlooked trait, guide what to look for.
- chemical reactivity: most
silicates relatively unreactive to simple tests.
- taste
- fuzzy rules that work a percentage of the
time.
What
determined the chemical make-up of the earth? The broad details
are fairly clear. The earth formed from meteorites, comets and
other early solar system debris circling the early sun. So certain
types of meteorites (chondrites) give us a clue as to what the
earth formed from, and what primitive compositions were. What
determined the chemical make-up of the early solar system debris?
Ultimately it is the stars we must look to. Stars are the thermo-nuclear
furnaces of the elements. For some elements super-nova reactions
are thought to be required. There are more details, if you want
to track them down, of what elements are produced by what types
of stellar reactions and stars.
What
determines the exact composition of an individual mineral?
- the composition of the fluids/solids it forms
from.
- the conditions of formation.
- note then that if we understand these two
factors then minerals can tell us about the conditions they formed
under. Specifically some mineral compositions can be paleothermomters
and paleobarometers.
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