FROODITE
Froodite – α-PdBi2 – is a very rare sulfide (an alloy of metalloids with Platinum Group Elements), of no importance as an ore.
It may contain Te.
1. Characteristics
Crystal system: Monoclinic prismatic.
Color: Gray. Highly reflective in silvery white. Tarnishes quickly.
Habit: Rounded grains.
Cleavage: {100} perfect, {001} distinct.
Tenacity: Brittle
Twinning: Sometimes.
Fracture: Irregular.
Mohs Hardness: 2.5
Parting: No.
Streak: Black.
Lustre: Metallic
Diaphaneity: Opaque.
Density (g/cm³): 12.05 – 12.6 (very high!)
2. Geology and Deposits
Froodite is known only from mill concentrates of copper ores rich in arsenic and lead. It is a magmatic sulfide from the Sudbury District (Ontario, Canada), where it was identified at the Frood Mine.
Its composition is similar to that of michenerite, which is associated with and much more common.
3. Mineral Associations
It is associated with common gangue minerals such as calcite.
It occurs with:
– common oxides (magnetite),
– common sulfides (chalcopyrite, galena, pentlandite, pyrrhotite),
– rare sulfides (talnakhite, mooihoekite),
– native elements (gold, silver, bismuth).
In the specific paragenesis there are:
– Pd minerals (cabriite, paolovite, michenerite, moncheite),
– Pt minerals (geversite, maslovite, sperrylite, niggliite, moncheite, insizwaite),
– Te minerals (hessite, altaite).
4. Transmitted Light Microscopy
This does not apply, as froodite is completely opaque.
5. Reflected Light Microscopy
Sample preparation: Froodite acquires a good polish.
PLANE POLARIZED LIGHT – PPL
Reflection color: Light creamy white.
Pleochroism: Creme a amarronzado.
Reflectivity: 57,13 – 59,87% (very high!)
Bireflectance: No.
CROSSED POLARIZED LIGHT – XPL
Isotropy / Anisotropy: Strong anisotropy between light gray and dark gray.
Internal reflections: No.
May be confused with: No information available.
General Characteristics:
Grain shape: Froodite occurs in rounded grains.
