Opalized Lungfish Tooth Plate

April 05, 2023




Photographer: Mila Zinkova   

Summary Author: Mila Zinkova   

Featured above is a 100 million years old opalized lungfish tooth plate with gem colors. It was found at Lightning Ridge in New South Wales, Australia. Note that the tooth plate is semi-transparent. This specimen was broken into four pieces by a miner. I put the pieces together to take the photo. The bottom photo was taken under a microscope and shows beautiful colorization and detail of the preservation of the inner structure of the tooth plate.

Opalization of plants and animal remains can occur in two ways, and at Lightning Ridge a combination of the following two processes is seen in many specimens.

  • Internal details not preserved (‘jelly mold’ fossils). Opal starts as silica dissolved in water. When the silica solution fills an empty cavity left by a shell or bone that’s rotted away – like jelly poured in a mold – it may harden to form an opalized cast of the original object. In these fossils, outside features can be beautifully preserved, but the internal structures are not recorded.
  • Internal details preserved. If the silica seeps into the organic material before it decomposes, then the organic molecules can be replaced by silica. This preserves very fine details of structures inside the bone or plant. When the silica is transparent, this internal anatomy is visible from the outside - the fossil is ‘see through’. 

Clearly in this specimen the second type of opalization took place.

Lungfish are basically living fossils. They’ve changed little since the time of dinosaurs. Unlike other fish that have only gills, lungfish can surface and take a breath of air. So, they may be able to survive when other fish cannot if water is lacking sufficient oxygen. In fact, much like many sea mammals, lungfish are obligate air breathers—they have to breathe air above water periodically to survive. Click here to see a video of other microscopic images that show the amazing play-of-color of the tooth plate.


Lightning Ridge, New South Wales, Australia Coordinates: -29.433333, 147.966667

Related Links:

Color in Opals

Australian Opal Centre