Staurolite, is an iron–aluminium silicate commonly found in schists and gneisses formed by regional metamorphism of argillaceous sedimentary rocks. Most regionally metamorphosed rocks occur in areas that have undergone deformation during an orogenic (Mountain building) event resulting in mountain belts that have since been eroded to expose the metamorphic rocks. The site you are standing at is apart of the Mt. Isa Orogen.
Staurolite forms when shale is strongly altered by regional metamorphism. It is often found in association with garnet, muscovite, and kyanite - minerals that form under similar temperature and pressure conditions.
Staurolite is a silicate (made of silicone & oxygen) mineral with a chemical composition of (Fe,Mg)2Al9Si4O23(OH). It is usually brown or black in colour with a resinous to vitreous lustre (Glass like shine).
Staurolite is usually easy to identify when it occurs as visible grains in a metamorphic rock. Grains of staurolite are typically larger than the grains of other minerals in the rock, and they often exhibit an obvious crystal structure. They occur as six-sided crystals, often with penetration twins.
The name "staurolite" is from the Greek word "stauros," which means "cross." The mineral commonly occurs as twinned, six-sided crystals that sometimes intersect at 90 degrees to form a cross. (An intersection angle of 60 degrees is more common.) When twinning occurs the crystals that are formed are referred to as Fairy Crosses or Maltese Crosses.
Staurolite is one of the index minerals that are used to estimate the temperature, depth, and pressure at which a rock undergoes metamorphism, other than that there are no commercial applications where Staurolite is used. Fairy or Maltese crosses as they are known locally are collected by mineral collectors, tourists as souvenirs and some believe they bring good luck or act as protection talismans. We think they are a neat example of how fascinating our world is.
The posted coordinates are at fossicking area were Staurolite is regularly found, we have also listed a second fossicking site which has also been a reliable source of Staurolite if you are keen to find some. If you don’t wish to keep anything you find and you don’t dig, it is possible to wander around and answer these EC questions without a permit, but if you are serious about finding a cross and keeping it, we highly recommend getting a QLD fossicking permit. Permit link here
To claim a find on this EarthCache we require you to:
1. Post a photo of you or something that identifies you/your team at GZ or WP2.
2. At either of the two locations, describe the land form around you.
3. The fairy crosses have come from a source, take a guess as to which direction have them come from, in your opinion, is there anything to indicate how you think they have ended up here?
4. If you are lucky enough to find a cross or part of a cross describe it. (refer to the pictures above to help you identify what you find)