2
Clinkers are composed of former sedimentary rocks
that laid under and over coal seams, that surrounded coal
seams that have been pyro-metamorphized due to exposure
to extreme temperatures. The coal seam would catch fire at
an exposed surface juncture through various means rang-
ing from spontaneous-combustion as a result of the break-
down of pyrite, to wildfires or lightning strikes igniting the
exposed coal. The fire would spread underground, burn-
ing up to temperatures of 1000°F [5] and drawing oxygen
through fractures in the rock. The intense heat would burn
away organic material from the surrounding sedimentary
rocks, as well as melting silica and clay minerals to form
glasses. Iron minerals in the sedimentary rocks would oxi-
dize, giving the rocks a reddish orange to yellowish appear-
ance (Figure 2). Their also resistant to weathering, and
commonly occur as either capstone outcrops that can act as
buffers to erosion for underlying coal and resource deposits,
or they can present as thick bed deposits that overly and
underly burned coal seams (Figure 3).
Currently, clinkers are used industrially as aggregate for
road and construction purposes and some specific clinkers
are refined down to powders as additives for glass and metal
working processes [9].
Critical minerals and REE (Rare Earth Elements) are
vital to modern technologies, and are used in electronics
computer chips, processors and other vital components.
The growing world population and ever advancing tech-
nologies require an increased demand of critical minerals
resources. Domestic geological features within the United
States are currently being looked at as potential sources of
domestic production of critical minerals and REE, reduc-
ing the need for importation from overseas markets.
We hypothesis that the pyro-metamorphization of
the sedimentary rocks could have caused a change in the
chemical characteristics of the pyro-metamorphized rocks,
potentially making them a source of REE and other critical
minerals that can be mined domestically.
METHODS OF STUDY
The methods used to research the hypothesis is the collec-
tion of clinker samples from around the San Juan Basin for
analysis purposes. Samples were submitted to a laboratory
for whole rock and trace element chemistry to provide a
clear picture of what elements and minerals are present and
in what concentrations to determine the economic viability
for the clinkers to contain REE and other critical minerals.
Petrography aids in identifying minerals present within the
rocks that correlate with the chemical analysis, and provide
insight into how the pyro-metamorphization affected the
rock and its internal structure. XRD (X-Ray Diffraction)
provides insight into what minerals are present in the rock
as well as identify minerals that could not be identified in
the petrographic analysis. Electron microprobe analysis
(EMPA) will be conducted in the future to confirm the
chemical analysis in the future.
CHEMISTRY RESULTS
When we compare the coal to the clinker, we can see very
similar chemistries. In comparison to chondrite normaliza-
tion [8], coal (Figure 4) and clinker (Figure 5) are slightly
enriched in LREE while being average or slightly depleted
in Heavy Rare Earth Elements HREE.
Clinker chemistry has been normalized to Average
European Shale and Average Upper Crust for Sedimentary
Rock standards to give an idea of how the clinkers com-
pare to other sedimentary deposits. This lets us see whether
the clinkers are enriched or depleted compared to other
rock types from around the world, giving an idea of their
Figure 2. Red Dog Fm Clinker rock, El Segundo Mine
Figure 3. Clinker beds transitioning into Coal beds, Left to
right, San Juan Basin
Clinkers are composed of former sedimentary rocks
that laid under and over coal seams, that surrounded coal
seams that have been pyro-metamorphized due to exposure
to extreme temperatures. The coal seam would catch fire at
an exposed surface juncture through various means rang-
ing from spontaneous-combustion as a result of the break-
down of pyrite, to wildfires or lightning strikes igniting the
exposed coal. The fire would spread underground, burn-
ing up to temperatures of 1000°F [5] and drawing oxygen
through fractures in the rock. The intense heat would burn
away organic material from the surrounding sedimentary
rocks, as well as melting silica and clay minerals to form
glasses. Iron minerals in the sedimentary rocks would oxi-
dize, giving the rocks a reddish orange to yellowish appear-
ance (Figure 2). Their also resistant to weathering, and
commonly occur as either capstone outcrops that can act as
buffers to erosion for underlying coal and resource deposits,
or they can present as thick bed deposits that overly and
underly burned coal seams (Figure 3).
Currently, clinkers are used industrially as aggregate for
road and construction purposes and some specific clinkers
are refined down to powders as additives for glass and metal
working processes [9].
Critical minerals and REE (Rare Earth Elements) are
vital to modern technologies, and are used in electronics
computer chips, processors and other vital components.
The growing world population and ever advancing tech-
nologies require an increased demand of critical minerals
resources. Domestic geological features within the United
States are currently being looked at as potential sources of
domestic production of critical minerals and REE, reduc-
ing the need for importation from overseas markets.
We hypothesis that the pyro-metamorphization of
the sedimentary rocks could have caused a change in the
chemical characteristics of the pyro-metamorphized rocks,
potentially making them a source of REE and other critical
minerals that can be mined domestically.
METHODS OF STUDY
The methods used to research the hypothesis is the collec-
tion of clinker samples from around the San Juan Basin for
analysis purposes. Samples were submitted to a laboratory
for whole rock and trace element chemistry to provide a
clear picture of what elements and minerals are present and
in what concentrations to determine the economic viability
for the clinkers to contain REE and other critical minerals.
Petrography aids in identifying minerals present within the
rocks that correlate with the chemical analysis, and provide
insight into how the pyro-metamorphization affected the
rock and its internal structure. XRD (X-Ray Diffraction)
provides insight into what minerals are present in the rock
as well as identify minerals that could not be identified in
the petrographic analysis. Electron microprobe analysis
(EMPA) will be conducted in the future to confirm the
chemical analysis in the future.
CHEMISTRY RESULTS
When we compare the coal to the clinker, we can see very
similar chemistries. In comparison to chondrite normaliza-
tion [8], coal (Figure 4) and clinker (Figure 5) are slightly
enriched in LREE while being average or slightly depleted
in Heavy Rare Earth Elements HREE.
Clinker chemistry has been normalized to Average
European Shale and Average Upper Crust for Sedimentary
Rock standards to give an idea of how the clinkers com-
pare to other sedimentary deposits. This lets us see whether
the clinkers are enriched or depleted compared to other
rock types from around the world, giving an idea of their
Figure 2. Red Dog Fm Clinker rock, El Segundo Mine
Figure 3. Clinker beds transitioning into Coal beds, Left to
right, San Juan Basin