Ilmenite

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Ilmenite

 

Ilmenite is the most abundant oxide mineral found in Lunar rocks. This is good because it has a very useful composition (FeTiO3). Ilmenite is also the principal ore for titanium on Earth. We can easily (relatively) extract iron, oxygen, and titanium dioxide from ilmenite.

Abundance and distribution

  • Apollo 11 and Apollo 17 mare basalts are up to 15%-20% ilmenite (by volume)(Lunar Sourcebook, 140).
  • However, the overall distribution of ilmenite in Lunar basalts varies widely (Lunar Sourcebook, 140).
  • Generally most samples contain <2% ilmenite but some high-Ti mare basalts contained >10% ilmentite. (4, chapter X,M)

 

Physical properties

  • Magnetic properties (Handbook of Lunar Materials, 57)
    • Susceptibility (cm-3) = 0.031 / 0.44
    • Field strength (oersted) = – / 0.6
  • Ilmenite is paramagnetic. This is because of the Fe2+.

 

Chemical composition

  • While the overwhelming majority of ilmenite is iron-based, a small percentage (0%-6%) of ilmenite has magnesium instead (Lunar Sourcebook, 142).
  • Lunar ilmenites are typically mixtures of ilmenite (FeTiO3) with small amounts of geikielite (MgTiO3). (4, chapter X,M)

 

Mechanical separation

 

Refining

The reduction of ilmenite in a hydrogen atmosphere will produce several useful things. Here’s how it works:

FeTiO3 + H2 + Heat (1200C) —->Fe + TiO2 + H2O

In the end we get free iron, titanium dioxide (also called rutile) (which can be stored for further refining or used), and water vapor (which is split back into hydrogen and reused in the process). That’s the theory at least. I haven’t found any evidence of a working Lunar prototype. The process still needs lots of work.

  • Melting point = 1367 (deg C) (Handbook of Lunar Materials, 55)

 

Data

Proportion of ilmenite (volume %) from Lunar samples. (90-20μm, not including fused-soil and rock fragments) (Lunar Sourcebook, 123)

  • Apollo 11 – 6.5
  • Apollo 12 – 2.7
  • Apollo 14 – 1.3
  • Apollo 15 (Highlands) – 0.4
  • Apollo 15 (Mare) – 0.8
  • Apollo 16 – 0.4
  • Apollo 17 (Highlands) – 3.7
  • Apollo 17 (Mare) – 12.8
  • Luna 16 – 1.8
  • Luna 20 – 0.0
  • Luna 24 – 1.0

 

Analysis of ilmenite from rocks and soils (selected samples)(Lunar Sourcebook, 171-172)

 

  • Apollo 11 (Soil)(unknown rock types)
    • Iron oxide (FeO) by weight percent range: 32.39%
    • Average FeO by percent weight = 32.39%
    • Ratio of iron to magnesium [Fe/(Fe+Mg)] range = 0.63
  • Apollo 11 (High-K)(>0.3% K20)
    • Iron oxide (FeO) by weight percent range: 41.7% – 44.81%
    • Average FeO by percent weight = 43.83%
    • Ratio of iron to magnesium [Fe/(Fe+Mg)] range = 0.88 – 0.96
  • Apollo 11 (Low-K) (<0.11% K2O)
    • Iron oxide (FeO) by weight percent range: 45.1%
    • Average FeO by percent weight = 45.1%
    • Ratio of iron to magnesium [Fe/(Fe+Mg)] range = 0.97
  • Apollo 11 olivine
    • Iron oxide (FeO) by weight percent range: 44.1%
    • Average FeO by percent weight = 44.1%
    • Ratio of iron to magnesium [Fe/(Fe+Mg)] range = 0.92
  • Apollo 12 olivine (>10% MgO, <5% TiO2)(Low-Ti)(1.5-9% TiO2)
    • Iron oxide (FeO) by weight percent range: 40.5% – 46.7%
    • Average FeO by percent weight = 43.6%
    • Ratio of iron to magnesium [Fe/(Fe+Mg)] range = 0.82 – 1.00
  • Apollo 12 pigeonite [a form of pyroxene]  (<10% MgO, <5% TiO2) (Low-Ti)(1.5-9% TiO2)
    • Iron oxide (FeO) by weight percent range: 46.30% – 46.74%
    • Average FeO by percent weight = 46.52%
    • Ratio of iron to magnesium [Fe/(Fe+Mg)] range = 0.98 – 1.00
  • Apollo 12 ilmenite (<10%MgO, >5% TiO2)(Low-Ti)(1.5-9% TiO2)
    • Iron oxide (FeO) by weight percent range: 45.16% – 45.4%
    • Average FeO by percent weight = 45.28%
    • Ratio of iron to magnesium [Fe/(Fe+Mg)] range = 0.98 – 1.00
  • Apollo 14 (Aluminous, Low-Ti basalts)(>10% Al2O3, 2-5% TiO2)
    • Iron oxide (FeO) by weight percent range: 45.30%
    • Average FeO by percent weight = 45.30%
    • Ratio of iron to magnesium [Fe/(Fe+Mg)] range = 0.97
  • Apollo 15 olivine (>10% MgO, <5% TiO2)(Low-Ti)(1.5-9% TiO2)
    • Iron oxide (FeO) by weight percent range: 46.84%
    • Average FeO by percent weight = 46.84%
    • Ratio of iron to magnesium [Fe/(Fe+Mg)] range = 0.99
  • Apollo 17 basalt
    • Iron oxide (FeO) by weight percent range: 45.7%
    • Average FeO by percent weight = 45.7%
    • Ratio of iron to magnesium [Fe/(Fe+Mg)] range = 0.97
  • Luna 16 soil (unknown rock types)
    • Iron oxide (FeO) by weight percent range: 44.70% – 48.14%
    • Average FeO by percent weight = 46.42%
    • Ratio of iron to magnesium [Fe/(Fe+Mg)] range = 0.97 – 0.99
  • Luna 20 soil (unknown rock types)
    • Iron oxide (FeO) by weight percent range: 37.1% – 45.7%
    • Average FeO by percent weight = 41.4%
    • Ratio of iron to magnesium [Fe/(Fe+Mg)] range = 0.72 – 0.99

 

Abundance of ilmenite (percent volume) in Lunar materials (Handbook of Lunar Materials, 53)

  • Mare basalts = 0%-25% (high-Ti basalts contain more ilmenite than low-Ti)
  • Anorthositic rocks = trace only
  • Fragmental breccias (>25 micrometers across) = 2%-12% (depends on local rock type)
  • Crystalline breccias = 1%-2% (limited to highlands only)
  • Soil = 0.5%-5% (depends on local rock type)

 

Iron content (percent weight) in typical Lunar ilmenite (Handbook of Lunar Materials, 54)

  • Mare = 44.88%
  • Highland = 37.38%

 

FeO concentrations in opaques (mostly ilmenite)(percent weight)(Space Resources: Vol 3 Materials, 29)

  • High-Ti mare basalts = 14.9% – 45.7%
  • Low-Ti mare basalts = 44.1% – 46.8%
  • Highland rocks = 11.60% – 36.0%

 

Ilmenite in mare basalts (percent content) (Space Resources: Vol 3 Materials, 34)

  • Apollo 11 mean
    • Modal (thin slice analysis) = 14.5%
    • Normative (chemical analysis estimate) = 21.1%
  • Apollo 12 mean
    • Modal (thin slice analysis) = 10%
    • Normative (chemical analysis estimate) = 7.5%
  • Apollo 15 mean
    • Modal (thin slice analysis) = 2.6%
    • Normative (chemical analysis estimate) = 4.1%
  • Apollo 17 mean
    • Modal (thin slice analysis) = 20.4%
    • Normative (chemical analysis estimate) = 23.7%
  • Average = 11.5% (Space Resources: Vol 3 Materials, 35)
  • Average (minus Apollo 15) = 14.4% (Space Resources: Vol 3 Materials, 35)

 

Extraterrestrial Materials Processing and Construction (I forgot to write down the page number)

  • Mature mare-dominated soils = Ilmenite is virtually absent in size fractions greater than 0.2 mm
    • Mineral distribution becomes uniform in fractions <0.02 mm
    • Best enrichment technique is to discard particles >0.2 mm
  • Immature soil = decrease in ilmenite content if >0.02 sized particles are discarded

 

Lunar samples % ilmenite (randomly selected by me) (5)

  • Sample 10003 (Apollo 11 mare basalt) = 13.3-18.2%
  • Sample 12015 (Apollo 12 mare basalt) = 0%
  • Sample 14078 (Apollo 14 KREEP basalt) = 0.5%
  • Sample 15261 (Apollo 15 soil) = 0%
  • Sample 67747 (Apollo 16 highland basalt) = 1.5%
  • Sample 70215 (Apollo 17 high-Ti mare basalt) = 13-37%

 

Resources

  1. Lunar Sourcebook
  2. Handbook of Lunar Materials
  3. Space Resources: Vol 3 Materials
  4. Extraterrestrial Materials Processing and Construction
  5. LPI Lunar Sample Atlas

 

 

 

 

 

 

 

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