Andradite
A calcium–iron garnet that grew during alteration in CV chondrites such as Allende.
Key facts
- Formula
- Ca3Fe2(SiO4)3
- Family
- Silicates
- Crystal system
- Cubic
What it is
Andradite is a garnet in which iron, carrying a charge of three, fills the smaller metal sites. It forms where calcium-rich rock reacts with iron-bearing fluids.
Where it is found
In Allende and other oxidised CV chondrites it occurs with hedenbergite, wollastonite and fayalite in dark inclusions, chondrule rims and veins. These minerals formed on the parent asteroid, probably in warm fluids, millions of years after the CAIs.
How it is recognised
It is pale brown to yellowish in thin section and is identified by microprobe analysis.
Did you know?
Did you know?
A green variety of andradite, demantoid, is one of the most valued garnet gems.
Did you know?
Andradite in CV chondrites has been dated using the decay of manganese-53.