Plume: AKA Digit pattern science
Posted: Tue Aug 30, 2022 3:42 am
What are the rarest opal patterns?
"Starbursts or sunbursts are among the rarest. Other patterns include peacock tail, block, flagstone, jigsaw, stripes, broad flash and fan, to name just a few." somebody
The rarest patterns are NOT mentioned because those are the MOST desirable if not Australian. I have seen Plume Stars.
DIGIT PATTERN
CONCLUSION: This study has documented the macroscopic characteristics of digits, distinct aesthetic features observed in many natural opals from Ethiopia but rarely seen in specimens from other regions. We propose that these columns form vertically with their rounded ends pointing upward, and that larger patches of color formed before the matrix. The first step in our model is the deposition of a homogeneous layer of opal with juxtaposed vertical columns. Next, polygonization of the columns occurs. Then, an influx of fluid (probably less rich in silica) remobilizes this layer. The remobilization is most efficient at grain boundaries, separating the columns and rounding their edges. Finally, opal precipitates again between the partially dissolved columns, cementing them into a matrix of either common or play-of-color opal.
Digits have been reported in only one Australian sample (figure 2).
,,, reported from other deposits, such as Virgin Valley, Nevada (Gübelin and Koivula, 2005; Gaber, 2007).
https://www.gia.edu/gems-gemology/FA13- ... ns-rondeau
Magnifica, for sale
"Starbursts or sunbursts are among the rarest. Other patterns include peacock tail, block, flagstone, jigsaw, stripes, broad flash and fan, to name just a few." somebody
The rarest patterns are NOT mentioned because those are the MOST desirable if not Australian. I have seen Plume Stars.
DIGIT PATTERN
CONCLUSION: This study has documented the macroscopic characteristics of digits, distinct aesthetic features observed in many natural opals from Ethiopia but rarely seen in specimens from other regions. We propose that these columns form vertically with their rounded ends pointing upward, and that larger patches of color formed before the matrix. The first step in our model is the deposition of a homogeneous layer of opal with juxtaposed vertical columns. Next, polygonization of the columns occurs. Then, an influx of fluid (probably less rich in silica) remobilizes this layer. The remobilization is most efficient at grain boundaries, separating the columns and rounding their edges. Finally, opal precipitates again between the partially dissolved columns, cementing them into a matrix of either common or play-of-color opal.
Digits have been reported in only one Australian sample (figure 2).
,,, reported from other deposits, such as Virgin Valley, Nevada (Gübelin and Koivula, 2005; Gaber, 2007).
https://www.gia.edu/gems-gemology/FA13- ... ns-rondeau
Magnifica, for sale