15" Colorful, Polished Mookaite Jasper Section - Australia

 
 
 
 
This is a 15" wide section of vibrantly colored Mookaite jasper. One side has been polished to a mirror-like finish and the "back side" of the specimen has been left rough/uncut. There are a couple of unique features on this specimen, the first being the iridescence along one edge of the jasper. Another interesting feature is the presence of cavities throughout the jasper, each of which is encrusted in what appears to be a layer of druzy quartz. The largest cavity looks to have brecciated jasper fragments lining the walls.

Mookaite jasper is a stunning, multi-colored stone with vibrant hues of reds, yellow and purples formed from the fossilized remains of microscopic radiolarians. It is found in the 110 million year old Windalia Radiolarite formation which formed on a shallow, marine shelf. Mookaite is found as vibrantly colored nodules in certain beds of soft, white clay within the formation.

Radiolarite is a fine-grained, chert-like sedimentary rock that is composed predominantly of the microscopic remains of radiolarians. Radiolaria are tiny (1/10th mm), free-floating, Zooplankton that produce intricate mineral skeletons made of silica. When the radiolarians died their tiny silica based, skeletons settled on the bottom of the ocean and became covered in sediment (mud/clay)

As this sediment turned to sedimentary rock (a process known as diagenesis) the silica from the radiolarian skeletons pinching and coagulates into ribbons, nodules and other irregular concretions. These ribbons, nodules and concretions are the Mookaite within the clay layers. The coloration is due to other (mostly iron based) mineral impurities present along with the silica. So, technically Mookaite could be considered is a fossiliferous, sedimentary rock made out of the tiny skeletons of radiolarians.

Jasper is a term that can be applied to an opaque variety of chalcedony (light does not pass through it) The opaqueness is due to a much larger amount of impurities mixed with silica/quartz. Like agate it may form in a huge variety of colors, and is often multi-colored. In most cases, jasper will occur when silica-rich fluids permeate throughout a soft sediment or volcanic debris deposit. The fluids then crystallize around the particles/impurities, resulting in a cementation process. Most often, the impurities present determine the coloration of the deposit following solidification, however other factors can play a role in the color of what is now considered a jasper.
DETAILS
SPECIES
Quartz var. Jasper
LOCATION
Mooka Creek, Gascoyne Junction, Western Australia
FORMATION
Windalia Radiolarite
SIZE
15 x 6.1", up to 3.6" thick
SUB CATEGORY
ITEM
#132410