Yowah – Home of the Yowah Nut

‘Yowah Nuts’ are a sub species of Boulder Opal, they are typically small boulders about the size
of a walnut and are found in a unique formation consisting of a regular band containing nuts packed
in a conglomerate. The opal is found either as a central kernel, or as thin veins, surrounding an
ironstone centre or traversing the nut, without reaching the outer edge.



Although predominantly found in the vicinity of Yowah in an area of only 1.5 square
kilometres, nuts with gem opal kernels have been found at the Koroit Opal fields.
Formations of a similar type are found in lesser concentrations on the northern opal
fields where the miners generally refer to them as matrix opal.
Yowah is Queensland’s southern most opal field and is centred on the small town
of Yowah 40km north east of Eulo and 150km west of Cunnamulla. The Yowah
mines include Black Gate and Leopardwood; Koroit is an associated opal field 50
nautical miles northeast of Yowah and encompasses Boobara and Holloways mines.



Once the nuts have been removed from the ground they must be cleaned and sorted. This
means prying them from the conglomerate and/or slicing or cracking them open.
Yowah Nuts are mostly 1.5 to 3.5 centimetres in diameter, but they may be the size of a fist
and there have been reports of nuts as large as (Aussie Rules) footballs. The vast majority of
these small ironstone concretions are either solid or have hollowed centres and do not contain
any opal.
There are widely ranging estimates on the percentage of nuts that do contain opal. The late
Dr.Ted Pough (1976) estimated 7-10 percent contain opal, but he did not specify the number
of nuts that contain precious opal. It is safe to say that out of every hundred nuts cracked
only a few are considered gems.



Every yowah nut is unique and those that contain precious opal make magnificent
specimens and gems, while the ‘duds’ are fascinating for mineral collectors.
Often the nuts are sliced as a conglomerate, revealing a number of different sized
nuts and various patterns of opalisation within a matrix - the results are marvellous
works of art!



The miner and cutter of these nuts and other such matrix formations get to
know the materials and what to expect, beautiful sets can be made with 4
or more slices obtained from a nut. As they are often naturally flawed with
cracks or potch, nuts containing Gem Opal kernels are very rare, the
rough is general precisely sawn in half to reveal two faces or it is expertly
hewn with a geo-hammer and may cleave conveniently in two.

Opalised wood is another sub species of Boulder opal for which Yowah and the surrounding opal fields are renowned, wood replacement does also occur at various opal fields across Queensland.

Boulder Opal Matrix is a generic term which can be used to describe the banded growth or leafed inclusion of precious opal with and/or in the ironstone host rock. The wondrous mixture of ironstone and flecks or veins of colourful opal creates endless patterns and designs, referred to as ‘picture stones’ or ‘fun stones’, these are eminently collectable. Because it is iron impregnated Boulder Opal Matrix is often the very hardest opal and has a beautiful lustre when polished, it is very well suited for use as beads or gemstones.