The
semi-precious stones are sometimes advertised as "Mookite",
"Mookalite" or "Mookarite."
Mookaite
is the common, or popular, name for the rock with the geological name
Windalia Radiolarite, being a fine grained, silicified and multi-coloured,
radiolarian siltstone, found in outcrops, principally on Mooka Station
(a sheep farm of around 700,000 acres)on the west side of Kennedy Range
in Western Australia.
Mookaite
comes in an array of colours. Red, white and yellow being the predominant
colours, but also, bone/ivory, orange, purple, maroon, pink, crimson,
mustard, as well as many variations on these. However the red, white
and yellow can often be found as significant single colour patches in
any particular rock.
Mookaite
is found only in Australia and is actually a fossiliferous sedimentary
rock & it is reasonably common to find cavities left by decomposed
belemnite casts or in some rare cases , impressions of ammonites. (Windalia
Radiolarite) Microscopic examination shows this rock consists of the
remains of tiny organisms known as radiolaria that have an unusual skeletal
structure of opaline silica.
Billions of these little critters were
deposited as sediment in the shallow areas of ancient sea beds. When
the seas retreated, these sediments were cemented into solid rock by
silica carried in groundwater. The type and degree of silicification
varies from place to place, forming opalite, chert and chalcedony.
It has been found in many very bright colors, reds, purples, tan, snow
white, ivory white, pinks and many other shades.
Sometimes
but not often it will have black dendrites and in the hands of a careful
lapidary the
cabochons can be stunning especially if you get very lucky and run
into a nice dendrite tree. The
more scenic the more these cabochons will bring. A hundred dollars
is common for a nice dendritic stone.