Agglutinates

Agglutinates are particles composed of mineral grains, glasses, rocks, and other agglutinates that are bonded together by melted glass. Within each agglutinate are very small particles of pure iron (along with a bunch of other important stuff) and chunks of iron bearing minerals. That makes agglutinates a prime target for iron extraction.

Agglutinates are created by impacts and always contain fine particles of Fe and FeS. An impacting meteoroid creates an agglutinate about 5 times its mass (5, pg 269). Larger impactors create less agglutinates because the glass is dissipated as small droplets (5, pg 269). Micrometeoroids massing 5.5×10^-5 to 7.0×10^-8 g are responsible for the formation of the majority of agglutinates (5, pg 269).  How this happens is described on the Lunar Free Iron post.

 

Chemical composition

• Compositionally and morphologically extremely complex (5, pg 252).
• In addition to the iron, agglutinates also contain solar wind gases (including hydrogen and helium) in relatively high abundances (A Global Lunar Landing Site Study to Provide the Scientific Context for Exploration of the Moon, 439). We’re eventually going to want to recover these as well.
• Agglutinate glass is generally dark brown to black in color (Handbook of Lunar Materials, 65).
• Agglutinate samples are often more than 50% mineralic (5, pg 261).
• The chemical composition of individual agglutinates often reflect the composition of the underlying source material (5, pg 263)

 

Physical properties

• Density (g/cm³ at 293.2 K) =
• Magnetism
• Important temperatures
  • Forging temperature
  • Melting point (K) =
  • Boiling point (K) =
• Thermal conductivity (cal cm^-1 sec^-1 K^-1 between 273.2 and 373.2 K) =
• Agglutinates are extremely delicate and can be destroyed more easily than rock or mineral fragments of similar sizes (5, pg 275).

 

Availability

• Agglutinates make up a substantial portion of the Lunar soil, from 5% to 65% (Lunar Sourcebook, 298).
• The average is 25%-30% though (Lunar Sourcebook, 298).
• One study put agglutinate abundance at 45% -47% for fine soil (2, pg 432)
• Lunar Bases and Space Activities of the 21st Century states that the average is over 50% (Lunar Bases and Space Activities of the 21st Century, 500).
• The more mature a soil is (meaning the longer the soil is exposed to space weathering), the higher the agglutinate content. (5, pg 267)

 

Particle sizes

• They are larger than most of the Lunar soil particles.
• Agglutinate particles are the primary carriers of nanophase iron and are usually smaller than 1mm (A Global Lunar Landing Site Study to Provide the Scientific Context for Exploration of the Moon, 439).
• Most are extremely complex shapes. Some are bowl, ring, or donut shaped. (5, pg 263).
• Overall less vesicular than homogeneous glasses (5, pg 263)
• Agglutinates preferentially incorporate materials finer than 177 micrometers (5, pg 266)
• Fine-grained detrital materials in agglutinates are usually <125 micrometers and have a median size of close to 38 micrometers. (5, pg 267)
• Most unbroken agglutinates range from 178 micrometers to 250 micrometers. (5, pg 267)

 

Mechanical separation

Not needed for this phase of the project.

 

Refining

Not needed for this phase of the project.

 

Data

Petrographic description (percent volume) of agglutinates in a particular sample (Handbook of Lunar Materials, 67-68)

• Apollo 17 mare sample 71061.1
  • <20 micrometers = 17.0%
  • 20-45 micrometers = 17.3%
  • 45-75 micrometers = 13.0%
  • 75-90 micrometers = 17.3%
  • 90-150 micrometers = 9.3%
  • 150-250 micrometers = 11.8%
  • 250-500 micrometers = 10.0%
  • 0.5-1mm (visual) = 10.0%
• Apollo 17 mare sample (soil under boulder) 72441.1
  • <20 micrometers = 21.0%
  • 20-45 micrometers = 50.0%
  • 45-75 micrometers = 39.3%
  • 75-90 micrometers = 45.5%
  • 90-150 micrometers = 41.7%
  • 150-250 micrometers = 54.6%
  • 250-500 micrometers = 30.5%
  • 0.5-1mm (visual) = 20.0%
  • 2-4mm (visual) = 25.0%
  • 4-10mm (visual) = 25.0%

 

Average composition of soil (<10 to 45 micrometer)(unknown if by weight or volume)(2, pg 432)

• Mare (Apollo 11 and Apollo 12)
  • Agglutinates = 47%
  • Total pyroxene = 15%
  • Opx (orthopyroxenes) = 2%
  • Pigeonite = 6%
  • Mg cpx (clinopyroxenes) = 6%
  • Fe cpx (clinopyroxenes) = 1%
  • Plagioclase = 13%
  • Olivine = 2%
  • Ilmenite = 3%
  • Volcanic glass = 2%
  • Other = 3%
• Boundary (Apollo 15 and Apollo 17)
  • Agglutinates = 45%
  • Total pyroxene = 12%
  • Opx (orthopyroxenes) = 2%
  • Pigeonite = 5%
  • Mg cpx (clinopyroxenes) = 5%
  • Fe cpx (clinopyroxenes) = 1%
  • Plagioclase = 15%
  • Olivine = 3%
  • Ilmenite = 4%
  • Volcanic glass = 6%
  • Other = 2%
• Highland (Apollo 14 and Apollo 16)
  • Agglutinates = 47%
  • Total pyroxene = 7%
  • Opx (orthopyroxenes) = 3%
  • Pigeonite = 2%
  • Mg cpx (clinopyroxenes) = 1%
  • Fe cpx (clinopyroxenes) = 0%
  • Plagioclase = 34%
  • Olivine = 2%
  • Ilmenite = 1%
  • Volcanic glass = 2%
  • Other = 1%

 

FeO content of three agglutinates from Apollo 12 soil (units unknown) (5, pg 265)

• Sample 1 = 12.4
• Sample 2 = 18.3
• Sample 3 = 13.7

 

FeO content of agglutinate and non-agglutinate from Apollo 16 soil samples (percent weight) (5, pg 266)

• Sample 65701
  • Agglutinate
    • Wt. Fraction = 0.613
    • FeO = 6.61%
  • Non-agglutinate
    • Wt. Fraction = 0.387
    • FeO = 4.57%
• Sample 61241
  • Agglutinate
    • Wt. Fraction = 0.571
    • FeO = 6.58%
  • Non-agglutinate
    • Wt. Fraction = 0.429
    • FeO = 3.49%
• Sample 61501
  • Agglutinate
    • Wt. Fraction = 0.557
    • FeO = 6.57%
  • Non-agglutinate
    • Wt. Fraction = 0.443
    • FeO = 4.03%
• Sample 64421
  • Agglutinate
    • Wt. Fraction = 0.555
    • FeO = 6.07%
  • Non-agglutinate
    • Wt. Fraction = 0.445
    • FeO = 3.77%
• Bulk Soil
  • • Wt. Fraction = 1.00
    • FeO = 4.71%

 

Two broad categories of glass particles (5, pg 252)

• Essentially homogenous
• Agglutinates – extremely inhomogenous

 

Homogenous glasses (5, pg 253)

• Angular and jagged  mostly with some spheres, dumbbells, and other rotational forms. Smaller grain sizes only as it has to cool before it hit the ground.
• Some have detrital rock or mineral fragments as cores.
• Some have mineral fragments dispersed in them
• A few are hollow (gas and or water)
• Up to 30% vesicular

 

Homogenous glasses (5, 255)

• Wide variety of colors – colorless, white, yellow, green, orange, red, brown, black. Most are darker.
• Darker colors contain more Fe and Ti. Lighter contains more Al.
• Refractive index = 1.570-1.749. Increases with increasing Fe and Ti. Decreases with increasing Al.

 

Homogenous glasses (5, 257)

• 11 compositional types of homogenous glasses at Apollo 15 site.
• Green glass = 19.61% (std. dev 0.84) FeO
• Mare 1 = 15.83 (std dev 2.16) FeO
• Mare 2 = 18.83% (std dev 2.14) FeO
• Mare 3 = 21.10% (std dev 1.46) FeO
• Mare 4 = 19.93% (std dev 1.76) FeO

 

Homogenous glasses (5, pg 259)

• Apollo 14 Fra Mauro basalt
  • Highland basalt = 5.05% (st dev 2.28) FeO
  • Low K = 9.67% (st dev 1.88) FeO
  • Moderate K = 9.52% (st dev 1.31) FeO
  • High K = 10.25% (st dev 1.09) FeO
  • ‘Granite’ 1 = 3.49% (st dev 3.16) FeO
  • ‘Granite’ 2 = 6.67% FeO
  • Mare-type basaltic glass = 18.14% (st dev 2.93) FeO
  • Frau Mauro basaltic glass = 10.56% (st dev 1.37) FeO = major constituent is KREEP
  • Anorthositic gabbroic glass = 5.59% (st dev 1.00) = Highland basalt
  • Gabbroic anorthositic glass = 2.98% (st dev 1.51)
  • ‘Granitic’ glass = 1.79% (st dev 2.16)
  • Low-silica glass = 1.19%

 

Resources

1. Lunar Sourcebook
2. A Global Lunar Landing Site Study to Provide the Scientific Context for Exploration of the Moon
3. Lunar Bases and Space Activities of the 21st Century
4. Handbook of Lunar Materials
5. Lunar Stratigraphy and Sedimentology