A lovely specimen of Glauberite Crystals. Initially these specimens are clear when first fished out of the mud with cut and bloodied hands. They turn white after contact with the Oxygen in the air. The fossicker who fished this one told me the second day was worse when cuts on his fingers were roughed up again. This happens when feeling around deep in the mud for them. Great fun. This is a rare and unusual Aussie mineral. The last big one found in an old box.
Snowtown, South Australia, Australia.
7.5cm x 7.1cm x 5.4cm, 101g.
Sodium Calcium Sulfate.
Glauberite is a mineral known better for when it is not there, than from when it is there. What does that mean? Well Glauberite is often pseudomorphed and “cast” by other minerals. A pseudomorph occurs when a mineral is replaced by another mineral at such a slow pace, essentially atom by atom, that no deteriorating effects occur to the shape of the crystal. The pseudomorph (meaning false shape) may look like Glauberite’s crystals but it is actually another mineral or even opal in one occurrence. Several minerals have been found to replace Glauberite such as calcite, quartz, gypsum and as mentioned, opal.
Glauberite also becomes cast by several minerals. It is soluble in water and probably this is the reason for this tendency. After Glauberite forms other minerals grow on top of the crystals. Later the Glauberite dissolves away, leaving a cast of itself as the only evidence of its past presence. Its crystal habit is unique enough that both pseudomorphs and casts can usually be identified as being produced from a Glauberite crystal. Some Quartz and Prehnite casts from Paterson, New Jersey were once thought to belong to a strange mystery mineral that no longer exists at the site. But most of these casts are now confidently assigned as Glauberite casts.