THE TECHNIQUE OF MACROPHOTOGRAPHY IN CATHODOLUMINESCENCE STUDIES

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THE TECHNIQUE OF MACROPHOTOGRAPHY IN
CATHODOLUMINESCENCE STUDIES

• By
• Donald J. Marshall, RELION Industries
• With acknowledgment to
• Dr. Anthony N. Mariano, Consultant

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MACROPHOTOGRAPHY

• MICRO vs MACRO
• CLASSICAL DEFINITION IS A PHOTO BIGGER THAN LIFE
• DOESNT WORK FOR MICROSCOPISTS BECAUSE ALL PHOTOS
  ARE LIKE THIS
• SO MACROPHOTOGRAPHY MEANS, TO US, ONLY CAMERA IS
  USED AND LARGE SPECIMEN AREA IS VIEWED

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MACROPHOTOGRAPHY

• Used only by a few investigators
• Microscope with very low magnification objective
  (1X) sometimes used
• But usually no microscope only a camera.
• Viewed area 2 to 5 cm in diameter

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WILLIAM CROOKES, F.R.S.

• 1880. Philosophical Transactions of Royal Society
• .preparation of sulphide of calcium. shines
  with a bright blue-violet light, and, when on a
  surface of several square inches, is sufficient
  to light up a room.

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MACRO vs MICRO

• Unfocused cold cathode beam about 1 cm.
  diameter.
• Top window in some cases limits viewed area to 7
  to 8 mm.
• So arbitrary dividing line is
• 5 mm or less is micro.
• 5 mm to 5 cm or greater is macro.

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OPERATIONAL REQUIREMENTS

• Capability to defocus the electron beam.
• Sufficient electron beam current to provide
  viewable cathodoluminescence.
• Large viewing window area.

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FOCUS and DEFOCUS

• Unfocused beam implies that nothing is done to
  the beam to change its size.
• Unfocused beam is usually not large enough in
  diameter only 0.5 cm to 1 cm.
• So defocusing is done.

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RASTERING

• Could also be done, in principle, by rastering
  beam but instrumentation requirements are more
  involved and this is not done on simple cold
  cathode-based instruments

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FOCUSING AND DEFOCUSING OF ELECTRON BEAM

• Requires special lens element in electron gun to
  defocus electron beam
• Both electrostatic and electromagnetic lens are
  possible.
• Electromagnetic lens is most common

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MAGNETIC FOCUS COIL
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FOCUSING AND DEFOCUSING

• In normal operation,
• focus point moves closer to coil (stronger
  focus) with higher coil current and
• Focus point moves away from coil (weaker focus)
  with lower coil current.

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DEFOCUSING MODE
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DEFLECTION, FOCUSING, AND ABERRATIONS

• Coils are usually designed for the best small
  spot size and shape.
• Coils are not designed for best defocused spot
  shapes and there is some appreciable variation in
  results.
• The spot can always be made larger but the shape
  may be less than circular or elliptical and some
  compromise is necessary.
• For those instruments which include magnetic
  deflection of the beam, there is an inevitable
  interaction between the deflection and focusing
  systems.
• Any deviations from the ideal beam shapes are
  termed aberrations. If there were sufficient
  demand for macro CL work, then coil designers
  would rise to the occasion.

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NO FOCUS CONDITION
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USUAL FOCUS CONDITION
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DEFOCUS CONDITION
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DEFOCUSED BEAM SHAPE EXAMPLE

• Scottish Sandstone
• Beam is large but it is strongly elliptical

5 cm
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Dr. James Clark

• Macro CL used originally to examine panned
  concentrates from stream sediments in carbonatite
  exploration.
• Used in granitoids where examination of larger
  areas facilitates identification of feldspar
  phase relationships and pathways for meteoric
  alteration fluids.
• Also to determine timing of quartz and carbonate
  events associated with gold mineralization and
  examination of cross cutting relationships in
  veins.
• Dr. James Clark, Applied Petrographics.
• http//www.appliedpetrographics.com

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GRANODIORITIC INTRUSIVE ROCK

• K feldspar - light blue CL - weak reddish purple
  overprint. Unaltered plagioclase - yellowish
  green overprinted by reddish brown to light brown
  CL with progressively stronger clay alteration.
• The K feldspar poikilitically encompasses smaller
  crystals of plagioclase.
• Quartz and micas are non-luminescent. Field of
  view 15.42 mm.
• Courtesy of Dr. James Clark

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GRANODIORITIC INTRUSIVE ROCK

• K feldspar light blue CL. Unaltered plagioclase
  yellowish green CL
• The K feldspar poikilitically encompasses
  smaller crystals of plagioclase.
• Quartz and micas are non-luminescent.
• Field of view 15.42 mm.
• Courtesy of Dr. James Clark

1. 5 centimeter
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MULTIPLE EPITHERMAL QUARTZ TYPES

• Epithermal quartz vein with CL
• CL photo shows two varieties of microcrystalline
  quartz (tan and dull red), while the
  comb-textured quartz has fine-scale growth zoning
  in shades of yellow, red, gray, and blue CL.
• Dr. James Clark

1.48 cm
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COMPLEX BANDED Q-CHALCEDONY VEIN
LATE STAGE CHALCEDONY AND QUARTZ

• Complex epithermal Q-chalcedony vein. CL photo
  highlights a quartz vein stratigraphy with early
  non-luminescent microcrystalline quartz (Q1), an
  intermediate stage of microcrystalline quartz
  with moderate yellowish-brown CL, and late-stage
  chalcedony and quartz with strong yellow CL (Q3).
  The main vein is cut by a narrow veinlet of Q2
  and orange-luminescent calcite.
• Dr. James Clark

EARLY NON-LUMINESCENT QUARTZ
CALCITE
2.14 cm
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DRUSY QUARTZ VEIN

• Drusy quartz in a polished slab of quartz vein
  material from an epithermal silver-gold mine,
  Durango, Mexico. Locally this quartz has native
  gold inclusions. No zonation visible in plane
  light.
• Kodak Royal Gold 200 film, 60 sec. 12.5 kV,
  0.6ma.
• Vertical dimension is 19 mm.
• Dr. James Clark

1.4 cm
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Quartz-calcite-adularia vein

• Quartz-adularia-calcite vein. Lattice- and
  parallel-bladed acicular calcite needles with
  interstitial quartz-adularia. Bright orange
  calcite overwhelms much weaker brown CL of
  adularia-quartz assemblage

1.54 cm
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Quartz-calcite-adularia vein

• Quartz-calcite-adularia vein. A band of
  lattice-bladed calcite has interstitial
  microcrystalline quartz-adularia. Microdrusy
  quartz partly lines voids within intersecting
  calcite blades. Calcite has bright orange CL and
  overwhelms the much subtler CL of adularia. The
  microdrusy quartz has zoned yellow CL (appears
  green in the photo).
• CL field of view 11.57mm.
• Courtesy of Dr. James Clark.

2 mm
1.2 centimeter
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DEWEY LIMESTONE

• Devonian from Oklahoma
• Macro provides a quick picture of the different
  major phases and serves as a guide to more
  detailed examination

5 cm.
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CORAL

• Solitary coral, Siphonophyllia Sp., Co. Sligo,
  perpendicular to long dimension.
• 14 kV, 1 m A, 2 seconds
• Sample from Claire Mulhall, Trinity College,
  Dublin

5 cm.
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2 mm
5 cm.
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CORAL

• Solitary coral, Siphonophyllia Sp., Co. Sligo,
  parallel to long dimension.
• 14 kV, 1 mA, 2 seconds
• Sample from Claire Mulhall, Trinity College,
  Dublin

5 cm.
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5 cm
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LIMESTONE DRILL CORE

• Partially dolomitised Waulsortian Limestone, Co.
  Tipperary
• 14 kV, 1 mA, 2 sec.
• Sample from Claire Mulhall, Trinity College,
  Dublin

5 cm.
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LIMESTONE DRILL CORE

• Limestone drill core expanded X2 to emphasize
  dolomite crystals

2.5 cm.
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MAP FOR MICRODRILLING

• Jay Kaufman, U. Md.
• Massive to finely laminated carbonate from
  Namibia.
• Determined Mn/Sr, 87Sr/86Sr,C and O isotopes from
  small selected areas.
• Kaufman et al., 1991, Precambrian Research, 49,
  p. 301
• Kaufman et al., 1993, Earth and Planetary Science
  Letters, 120, p.409

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MICRODRILLING OF LAMINATED CARBONATE

• MLM moderately luminescent microspar
• LSLC luminescent sparry calcite
• NLM non-luminescent microspar
• WR whole rock

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Map for microdrilling

• Jay Kaufman et al from proterozoic in Namibia.
• Drilled out samples from 1 mm diameter areas for
  C and O isotopic analyses
• WR whole rock value. Local values shown also

2.9 cm
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Map for microdrilling

• Jay Kaufman et al,
• Drilled out 1 mm areas for Mn/Sr and 87Sr/86Sr
  analyses.
• WR whole rock value. Local values shown also

2.9 cm
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Dr. Anthony N. Mariano

• Specialist in mineral deposits of all kinds and
  especially those associated with rare earths.
  Investigated them all over the world on five
  continents.
• Has been using CL for more than 30 years.
• Dr. Anthony N. Mariano, Carlisle, MA USA

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CARBONATITES

• Dr. Mariano uses macrophotos extensively in his
  work on carbonatites and especially likes to work
  with slabs.
• Slabs give you a better picture of what the rock
  really looks like and especially as an initial
  overall look. (Dr. Anthony Mariano)

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Apatite Søvite Okorusu, Namibia

• Light lilac pink CL apatite LREE activated
• Orange CL calcite, Mn2
• Non-CL - pyroxene
• 17 kV,0.8 mA
• All apatite in carbonatite are LREE

46 millimeters
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Søvite, Okorusu, Namibia

• Various stages of calcite crystallization showing
  variations in orange to orange-red CL,
  corresponding to changes in trace element content
  of calcite with each crystallization episode.
• Also blue fluorite

46 mm
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Nepheline Syenite, Okorusu, Namibia

• Light blue CL plagioclase
• Grey (non-CL) nepheline
• Dull red CL specks are sodalite
• Not a carbonatite

46 mm in length
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Fluorite ore and apatite, Okorusu, Namibia

• Hydrothermal mineralization of fluorite and
  apatite
• light blue zoned fluorite, intrinsic
• light lilac-pink apatite, LREE
• Really dark is quartz or voids.
• Dr. Anthony N. Mariano

46 mm
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Carbonatite, Matongo Bandaga, Burundi

• Blue apatite, LREE activators
• Bright red, fenite Fspars (Fe3)
• dark areas are blue non-luminescing pyroxenes
  (aegerine)
• Orange calcite
• Dr. Anthony N. Mariano

46 mm
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Contact between apatite magnetite søvite and
fenite, Okorusu, Namibia

• Fenite carbonatite contact
• knob on upper right side is Søvite with orange CL
  calcite, light blue CL apatite and non-CL
  magnetite. Band on left is dominant orange CL
  calcite that drowns out red, Fe3 activated CL,
  of K feldspar. In plane light band is leucocratic
  and in sharp contact with central melanocratic
  band. The light colored matrix is calcite and
  orthoclase and the dark green disseminated grains
  are diopside.
• The central band contains non-CL diopside and
  veins of dull grey CL celsian (activator not
  known). First reported occurrence of celsian
  (BaAlSi3O8) in carbonatite.
• Late bands are calcite
• 16 kV, 0.9 mA, 30 seconds, ASA
• Dr. Anthony N. Mariano

46 mm
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GEMSTONES

• Not surprisingly, gem stones are one of the
  favorite candidates for CL macrophotograpy.
• They are often large.
• They usually have an irregular, non-planar,
  shape.
• Often they are not removable from their mounts

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SYNTHETIC DIAMOND

• Synthetic diamond CL at room temperature
• Dr. C.M. Welbourn, Diamond Sales, Ltd.

5.1 millimeters
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SYNTHETIC DIAMOND

• Synthetic diamond CL at low temperatures, 80
  degrees K
• Dr. C. M. Welbourn, Diamond Sales, Ltd.

5.1 millimeters
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Dr. Johann Ponahlo

• Physical-chemist and gemologist.
• Has used CL macro macro techniques
  for description and documentation of natural and
  synthetic gemstones for more than two decades.
• Dr. Johann Ponahlo, Vienna, Austria

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• Samples of considerable thickness and/or of
  irregular shape can be studied as well as
  specimens in their original settings and even
  small figurines.
• Dr. Johann Ponahlo

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ZIRCONIA

• 30 carat zirconia
• 5 kV, 1 mA
• Dr. Johann Ponahlo

1.8 cm
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SYNTHETIC GADOLINIUM GARNET

• Synthetic gadolinium garnet 5.8 mm diameter, 3.7
  mm height.
• The CL spectrum consists of narrow bands of
  trivalent Eu and Tb.
• 5 kV, 1 mA
• Dr. Johann Ponahlo

5.8 mm
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CORUNDUM

• 12 carat synthetic corundum
• Sample is brown in natural light
• 5 kV, 1 mA
• Dr. Johann Ponahlo

1.5 cm
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AMAZONITE AND GROSSULARITE

• Yellow green is grossularite
• Blue is amazonite, 7.2 carat. Bands clearly
  identify sample as feldspar
• 8 kV, 1 mA
• Ponahlo

8 mm
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MOUNTED ALEXANDRITE

• Right Natural  gt20 carat  alexandrite in its
  setting from mine near the Takowaya river where
  alexandrites first discovered in 1830. Stone and
  setting date back to 19th century. Valued at 1.3
  million euros.
• Left 22 carats synthetic alexandrite made
  by Kyocera Inc., Japan (1990).
• Natural stone CL is distinctly lower than
  synthetic. Natural stone on display in Museum for
  Natural History, Vienna.
• Dr. Johann Ponahlo.

Synthetic is blue green in daylight and
violet-tinted in artificial light
1.4 cm
Valued at 1.3 million euros
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CHROMIUM DIOPSIDES FROM BRAZIL AND RUSSIA

• Two on right are natural diopsides from Brazil
• Four on left are natural diopsides from Russia.
• 9 kV, 0.7 mA
• Dr. Johann Ponahlo

2.5 cm
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COLORLESS TOPAZ, SCAPOLITE, LEUCOSAPPHIRE

• Upper left is leucosapphire
• Lower left is 4 carat scapolite
• Blue is 13 carat cut topaz
• 7.5 kV, 0.8 mA
• Dr. Johann Ponahlo

30 mm
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SAPPHIRE AND CATS EYE APATITE

• Both cabochons are nearly opaque and colorless.
• Red CL is a sapphire from Sri Lanka
• Yellow CL is Apatite
• 12 kV, 0.9 mA
• Dr. Johann Ponahlo

19.6 mm
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YULETIDE TREE

• Regardless of ones religious beliefs, a
  decorated Yule time evergreen is always a welcome
  sight. This particular tree was created by Skip
  Palenik, Microtrace Analytical, and his son
  Chris. The illumination comes from the
  cathodoluminescence of the various minerals that
  they arranged.

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MERRY XMAS FROM MICROTRACE ANALYTICAL

• Blue are zircon
• Green are plagioclase
• Pink is fluorapatite
• Red is calcite
• Arranged by Chris Palenik, Microtrace Analytical

9.2 mm
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ACKNOWLEDGMENTS

• Dr. James Clark, Applied Petrographics, Portland,
  OR
• Dr. Shane Elen, GIA, Carlsbad, CA
• Dr. Alan Kaufman, University of Maryland, College
  Park, MD
• Dr. Anthony Mariano, Carlisle, MA
• Dr. Claire Mulhall,Trinity College, Dublin
• Dr. Christopher Palenik, Microtrace Analytical,
  Elgin, IL
• Dr. Johann Ponahlo, Vienna, Austria
• Dr. George Sevastopulo, Trinity College, Dublin
• Dr. Chris Welbourn, DeBeers,UK

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BIBLIOGRAPHY

• Clark, Dr. James, Applied Petrographics,
  http//www.appliedpetrographics.com
• Crookes, William1880. Contributions of molecular
  physics in high vacua. Magnetic deflection of
  molecular trajectory, laws of magnetic rotation
  in high and law vacua, -phosphorogenic properties
  of molecular discharge. Philosophical
  Transactions of the Royal Society of London, vol.
  170, part II, 641-662.
• Kaufman, A.J., Jacobsen, S.B. and Knoll, A.H.
  1993. The Vendian record of C- and Sr-isotopic
  variations Implications for tectonics and
  paleoclimate.  Earth and Planetary Science
  Letters 120 409-430.Kaufman, A.J., Hayes, J.
  M., Knoll, A.H. and Germs, G.J.B. 1991. Isotopic
  compositions of carbonates and organic carbon
  from Upper Proterozoic successions in Namibia
  Stratigraphic variation and the effects of
  diagenesis and metamorphism.  Precambrian
  Research 49 301-327.
• Welbourn, C.M., M. Cooper, and P. M. Spear 1996.
  De Beers Natural versus synthetic diamond
  verification instruments, Gems and Gemology, p.
  156-169.