Halite
Rock salt, found as purple crystals with trapped water in two ordinary chondrites and as salts in the Bennu sample.
Key facts
- Formula
- NaCl
- Family
- Carbonates, sulphates, salts and weathering products
- Crystal system
- Cubic
What it is
Halite is sodium chloride, ordinary salt. It crystallises when salty water evaporates.
Where it is found
In 1998 purple and blue halite crystals were found in the Monahans H chondrite, which fell in Texas, and later in Zag, which fell in Morocco. Some contain tiny pockets of liquid salty water. Dating with iodine–xenon showed the salt formed within a few million years of the Solar System's birth, probably on a water-bearing body before being delivered to the H chondrite parent. Bennu samples also contain sodium chloride and other evaporite salts.
How it is recognised
In meteorites it is purple to blue, coloured by radiation damage from potassium-40 in neighbouring sylvite. It dissolves in water, so these meteorites must be kept dry.
Did you know?
The fluid inclusions in Monahans halite are some of the oldest liquid water ever sampled.
The purple colour comes from defects caused by billions of years of natural radiation.