Assignment #2 Mineral Evolution
Intro Geochem Spring 2019
Due Tuesday 2/5 - START OF CLASS (no late assignments)
Hazen, Robert M (2010) Evolution of Minerals. Scientific American, March 2010, 58-65
You will turn in your assignment at the beginning of class on discussion day. Bring an extra hard copy of
your completed assignment – and of the paper - to class that day to help with the discussion.
Note – It is critical that you avoid plagiarism while working on this. You should not be just pulling
information from the paper, but you should understand it and turn it into your own thoughts. That may
take more than 1 reading of the paper.
1. For each of the major time periods in Hazen (2010), summarize the following information in the
table at the end of this assignment. Do NOT copy the information from the paper*, but summarize it
in bullets or another abbreviated format.
2. To show how well you truly understand the different phases, write one tweet for each time period
(for a total of 5) that summarizes the main point for that time period. For this assignment, limit
yourself to the “classic” twitter rule of 140 characters.
3. The article discusses the processes that lead to redistribution of elements on the earth. In your own
words, explain why that is important in this context.
4. The definition of a mineral requires that it be “inorganic”. Discuss that requirement in the context of
this paper. Do you agree? Not agree? Your answer should be a well-constructed, thoughtful
paragraph that illustrates both your opinion and some detail from the paper.
5. Put the paper into context by creating a conceptual timeline of these stages. You need to include
the major time periods and how they are distinguished. You can do this by hand (it must be legible!)
or using a computer. This is an opportunity to explore creative ways of explaining scientific concepts.
This will be graded on originality, creativity, completeness & detail, and your ability to clearly
communicate the concept.
That would be considered plagiarism, but you all know how to avoid that!
Why is it
BY ROBERT M. HA ZEN
Only a dozen minerals (crystalline compounds) are known to
have existed among the ingredients that formed the solar
system 4.6 billion years ago,
but today Earth has more than
4,400 mineral species.
Earth’s diverse mineralogy developed over the eons, as new
came into play.
Remarkably, more than half of
the mineral species on Earth
owe their existence to life,
which began transforming the
planet’s geology more than
two billion years ago.
nce upon a time there were no minerals
anywhere in the cosmos. No solids of
any kind could have formed, much less
survived, in the superheated maelstrom following the big bang. It took half a million years before the first atoms— hydrogen, helium and a bit
of lithium— emerged from the cauldron of creation. Millions more years passed while gravity
coaxed these primordial gases into the first nebulas and then collapsed the nebulas into the first
hot, dense, incandescent stars.
Only then, when some giant stars exploded
to become the first supernovas, were all the other chemical elements synthesized and blasted
into space. Only then, in the expanding, cooling
gaseous stellar envelopes, could the fi rst solid
pieces of minerals have formed. But even then,
most of the elements and their compounds were
too rare and dispersed, or too volatile, to exist as
anything but sporadic atoms and molecules
among the newly minted gas and dust. By not
forming crystals, with distinct chemical compositions and atoms organized in an orderly array
of repeating units, such disordered material fails
to qualify as minerals.
Microscopic crystals of diamond and graph-
ite, both pure forms of the abundant element
carbon, were likely the first minerals. They were
soon joined by a dozen or so other hardy microcrystals, including moissanite (silicon carbide),
osbornite (titanium nitride), and some oxides
and silicates. For perhaps tens of millions of
years, these earliest few species —“ur-minerals”—
were the only crystals in the universe.
Earth today, in contrast, boasts more than
4,400 known mineral species, with many more
yet to be discovered. What caused that remarkable diversification, from a mere dozen to thousands of crystalline forms? Seven colleagues and
I recently presented a new framework of “mineral evolution” for answering that question.
Mineral evolution differs from the more traditional, centuries-old approach to mineralogy,
which treats minerals as valued objects with distinctive chemical and physical properties, but
curiously unrelated to time — the critical fourth
dimension of geology. Instead our approach uses
Earth’s history as a frame for understanding
minerals and the processes that created them.
We quickly realized that the story of mineral
evolution began with the emergence of rocky
planets, because planets are the engines of minM a r c h 2 0 10
Looking at the mineral kingdom through the lens
of deep time leads to a startling conclusion:
most mineral species owe their existence to life
w w w. S c i e n t i f i c A m e r i c a n . c o m
Robert M. Hazen, senior staff
scientist at the Carnegie Institution’s Geophysical Laboratory and
Clarence Robinson Professor of
Earth Science at George Mason
University, received his Ph.D. in
earth science at Harvard University
in 1975. He is author of 350 scientific articles and 20 books, including Genesis: The Scientific Quest
for Life’s Origin, and he frequently
presents science to nonscientists
through radio, television, public
lectures and video courses. Hazen’s
recent research focuses on the role
of minerals in the origin of life. The
mineral hazenite, which is precipitated by microbes in the highly
alkaline Mono Lake in California,
is named after him.
4.6 BILLION YEARS AGO: Millions of planetesimals form in the disk of dust and gas that
remains around the recently ignited sun (in background) and collide to form Earth
(glowing planet). More than 200 minerals, including olivine and zircon, develop
in the planetesimals, thanks to melting of their material, shocks from collisions,
and reactions with water. Many of these minerals are found in ancient chondritic meteorites.
W Olivine crystals in pallasite (meteorite)
eral formation. We saw that over the past four
and a half billion years Earth has passed through
a series of stages, with novel phenomena emerging at each stage to dramatically alter and enrich
the mineralogy of our planet’s surface.
Some details of this story are matters of intense debate and will doubtless change with future discoveries, but the overall sweep of mineral
evolution is well-established science. My colleagues and I are not presenting controversial new
data or radical new theories about what occurred
at each stage of Earth’s history. We are, rather,
recasting the larger story of that history in the
light of mineral evolution as a guiding concept.
I do, however, want to emphasize one intriguing insight: most of Earth’s thousands of minerals owe their existence to the development of life
on the planet. If you think of all the nonliving
world as a stage on which life plays out its evolutionary drama, think again. The actors renovated their theater along the way. This observation also has implications for the quest to fi nd
signs of life on other worlds. Sturdy minerals
rather than fragile organic remains may provide
the most robust and lasting signs of biology.
Planets form in stellar nebulas that have been
seeded with matter from supernovas. Most of a
nebula’s mass rapidly falls inward, producing
the central star, but remnant material forms a
vast rotating disk around the star. These
hese leftovers progressively clump into larger
larger bits: sand-, pebble- and fi st-size
fluff balls of primordial dust harboring
a limited repertoire of a dozen or so urminerals, along with other miscellaaneous atoms and molecules.
Dramatic changes occur when
the nascent star ignites and bathess the nearby
concentrations of dust and gas with a refi ning
fire. In our own solar system, stellar ignition occurred almost 4.6 billion years ago. Pulses of heat
coming from the infant sun melted and remixed
elements and produced crystals representing
scores of new minerals. Among the crystalline
novelties of this earliest stage of mineral evolution were the fi rst iron-nickel alloys, sulfides,
phosphides, and a host of oxides and silicates.
Many of these minerals are found in the most
primitive meteorites as “chondrules”: chilled
droplets of once molten rock. (These ancient
chondritic meteorites also provide the evidence
for the ur-minerals that predated chondrules.
Mineralogists find the ur-minerals in the form of
nanoscopic and microscopic grains in the
In the ancient solar nebula, chondrules quickly clumped into planetesimals, some of which
grew to more than 100 miles in diameter— large
enough to partially melt and differentiate into
onionlike layers of distinctive minerals, includM a r c h 2 0 10
COURTESY OF THE TEACHING COMPANY (Hazen); RON MILLER (illustrations); NATURAL HISTORY MUSEUM, LONDON (pallasite);
SCIENTIFICA Getty Images (zircon); MASSIMO BREGA Photo Researchers, Inc. (chondrite)
n the 4.6 billion years since the
solar system formed, the suite of
minerals present has evolved from
modest beginnings — about a dozen
minerals in the presolar nebula —
to better than 4,400 minerals
found on Earth today. The planet
has passed through a series of
stages, represented at the right
and in the following pages by five
snapshots, involving a variety of
mineral-forming processes. Some
of these processes generated
completely new minerals, whereas
others transformed the face of the
planet by turning former rarities
into the commonplace.
BIOPHOTO ASSOCIATES Photo Researchers, Inc. (lepidolite); SCIENTIFICA Getty Images (beryl); JACANA Photo Researchers, Inc. (tourmaline)
4.4 BILLION YEARS AGO: The surface of lifeless Hadean Earth is largely black basalt, a rock
formed from molten magma and lava. The next two billion years see about 1,500 minerals
produced. Repeated partial melting of rock concentrates scarce, dispersed elements such as
lithium (found in lepidolite), beryllium (in beryl) and boron (in tourmaline). Chemical reactions
and weathering by the early oceans and the anoxic atmosphere also contribute. Minerals formed
under high pressure, such as jadeite, are brought to the surface by plate tectonics.
ing a dense, metal-rich core. Frequent collisions
in the crowded solar suburbs introduced intense
shocks and additional heat, further altering the
minerals in the largest planetesimals. Water also
played a role; it had been around from the beginning, as ice particles in the presolar nebula, and
in the planetesimals these melted and aggregated
in cracks and fissures. Chemical reactions with
the resulting water generated new minerals.
Perhaps 250 different mineral species arose
as a consequence of these dynamic planet-forming processes. Those 250 minerals are the raw
materials from which every rocky planet must
form, and all of them are still found today in the
diverse suites of meteorites that fall to Earth.
Primordial Earth grew ever larger. Big planetesimals swallowed smaller ones by the thousands
until only two major rivals remained in our orbital zip code, the proto-Earth and a much smaller
Mars-size body sometimes known as Theia, after
the mother of the Greek goddess of the moon. In
a final paroxysm of unimaginable violence, Theia sideswiped the proto-Earth, vaporizing its outer layers and blasting 100 million trillion tons of
incandescent rock vapors into space to become
the moon. This scenario explains the high angular momentum of the Earth-moon system and
many unusual features of the moon, including
why its bulk composition matches that of Earth’s
w w w. S c i e n t i f i c A m e r i c a n . c o m
rare “incompatible” elements.
mantle (the nearly 2,000-mile-thick layer that
extends from Earth’s iron-nickel core to the
three- to 30-mile-thick crust at Earth’s surface).
Following this moon-spawning collision
about 4.5 billion years ago, the molten Earth began the cooling that continues to this day. Although Earth’s primitive surface included dozens of rare elements— uranium, beryllium, gold,
arsenic, lead and many more— that were capable
of forming a diverse assortment of minerals,
Theia’s impact had served as a cosmic “reset.” It
left Earth’s outer layers thoroughly mixed, with
these less common elements far too dispersed to
form separate crystals. Our planet was a desolate, hostile world, incessantly bombarded by
nebular debris and largely covered by a veneer of
black basalt, a kind of rock that is formed even
in modern times when lava solidifies.
Earth’s mineralogical diversity gradually increased through the aptly named Hadean eon
(prior to about four billion years ago), primarily
from repeated melting and solidifying of the
rocky crust, as well as from weathering reactions
with the early oceans and atmosphere. Over
countless cycles, this partial melting and resolidifying of volumes of rock, and interactions between rock and water such as the dissolution of
selected compounds, gradually concentrated uncommon elements enough to form new generations of exotic minerals.
Not every planet possesses this great mineralSCIENTIFIC AMERICAN
In a geologic
instant, photosynthesis by
new kinds of
about the Great
formin potential. Tiny, dehydrated Mercury
Earth’s equally dry moon became frozen before much
melting could occur. Consequently,
that no more than about 350 differest
ent mineral species will be found on those
worlds. Mars, with a modest water budget,
might have fared a little better as a result of
species such as clays and evaporite
that form when oceans dry up. We esmine
timate that NASA probes might eventually identify as many as 500 different minerals on the
Ear is bigger, hotter and wetter and thus has
other mineral-forming tricks to play. All the
a few o
rocky planets experienced volcanism that poured
basalt across their surfaces, but Earth (and maybe
Venus, which is about equal in size) had enough
inner heat to remelt some of that basalt to form a
suite of igneous rocks called granitoids, including
the familiar tan and gray granites of curbstones
and countertops. Granites are coarse-grained
blends of minerals, including quartz (the most
ubiquitous grains of sand at the beach), feldspar
(the commonest of all minerals in Earth’s crust),
and mica (which forms shiny, sheetlike mineral
layers). All these minerals were produced earlier
in very small quantities in large planetesimals, but
they first appear in great abundance in Earth’s
geologic record thanks to the planet’s graniteforming processes.
On Earth, repeated partial melting of gran-
W Fossil stromatolite
ites concentrated rare “incompatible” elements that are unable to
find a comfortable crystallographic home in common minerals. The resulting
rocks feature more than 500 distinctive minerals, including giant crystals of species rich in
lithium, beryllium, boron, cesium, tantalum,
uranium, and a dozen other rare elements. It
takes time — some scientists estimate more than
a billion years — for these elements to achieve
mineral-forming concentrations. Earth’s planetary twin, Venus, may have been sufficiently
active for long enough to progress this far, but
neither Mars nor Mercury has yet revealed significant surface signs of granitization.
Earth gained even more mineral diversity
through the planetary-scale process of plate tectonics, which generates fresh crust along chains
of volcanoes, while old crust is swallowed up in
subduction zones, where one plate slips under another and is returned to the mantle. Immense
quantities of wet, chemically diverse rocks subducted from the crust were partially melted,
causing further concentration of scarce elements.
Hundreds of new minerals were produced in
massive sulfide deposits, which today provide
some of Earth’s richest bodies of metal ore. Hundreds more mineral species first appeared at
Earth’s surface when tectonic forces uplifted and
exposed deep rock domains with their hoard of
distinctive minerals that form under high presM a r c h 2 0 10
RON MILLER (illustrations); SCIENTIFICA Getty Images (rhodonite); TED KINSMAN Photo Researchers, Inc. (stromatolite);
E. R. DEGGINGER Photo Researchers, Inc. (turquoise)
2 BILLION YEARS AGO: Photosynthetic living organisms have given Earth’s atmosphere a
small percentage of oxygen, dramatically altering its chemical action. Ferrous (Fe2+) iron
minerals common in black basalt are oxidized to rust-red ferric (Fe3+) compounds. This
“Great Oxidation Event” paves the way for more than 2,500 new minerals, including
rhodonite (found in manganese mines) and turquoise. Microorganisms (green) lay down
sheets of material called stromatolites, made of minerals such as calcium carbonate.
COURTESY OF ALAN JAY KAUFMAN (cap carbonate); TED KINSMAN Photo Researchers, Inc. (kaolinite); SCIENCE SOURCE Photo Researchers, Inc. (snow crystal)
700 MILLION YEARS AGO: Climate change covers the entire planet surface with one
mineral — ice — for millions of years. Eventually carbon dioxide from volcanoes
triggers runaway global warming, and the planet cycles between hothouse and
snowball. In the hothouse phases, weathering adds large quantities of fi negrained clay minerals such as kaolinite to the landscape. Distinctive “cap carbon-ate” layers deposited in shallow, warming oceans include crystals six feet tall.
sure, such as jadeite (one of two minerals better
known as the gemstone jade).
All told, perhaps 1,500 different minerals
found on or near Earth’s surface might have
been generated by dynamic crust and mantle
processes during Earth’s first two billion years.
But mineralogists have catalogued more than
4,400 different mineral species. What happened
to triple Earth’s mineralogical diversity?
The answer is life. The biosphere distinguishes
Earth from all other known planets and moons,
and it has irrevocably transformed the nearsurface environment— most conspicuously the
oceans and atmosphere but also the rocks and
Life’s earliest manifestations— primitive single-celled organisms that “fed” on the chemical
energy of rocks — cannot have had much effect
on Earth’s mineralogical diversity. To be sure,
geologists have found biologically mediated
rock formations dating back to 3.5 billion years
ago, including reefs made of calcium carbonate
and so-called banded iron formations (in which
iron oxides apparently lock away the fi rst oxygen produced by life). But the land was still barren, the atmosphere at large still lacked oxygen,
surface weathering was slow, and the earliest life
contributed almost nothing to alter the number
of minerals present or their distribution.
w w w. S c i e n t i f i c A m e r i c a n . c o m
S Cap carbonate
That situation changed
d iin a geologic
l i iinstant
with the rapid ri ...
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