PDS_VERSION_ID        = PDS3
RECORD_TYPE           = STREAM

OBJECT                = TEXT
  PUBLICATION_DATE    = 2009-11-15
  NOTE                = "Sample description"
END_OBJECT            = TEXT
END

SW rift zone, downwind of the caldera.

High-level Description: Opaline weathering on 2-month-old, freshly-cut
fine-ash surface. Light-grey ash occurs in layers alternating between fine and
coarse. Weathering has caused some oxidation of iron, resulting in rust-red
staining around the edges of the fresh surface. Opal deposits are already
forming on sharp edges and elevated surfaces, however, opal is not very dense.


Silica-rich coating occurs as hemisphere-shape clusters, which tend to be
clustered together. On ash with larger, more angular surfaces, opal is
concentrated on sharp edges. Most opal clusters are 1 mm or smaller.
Smaller-grained layers show preferential growth (possibly through wicking
action during water percolation). Larger-grained layers may lead to less
connected pore space (even though the percentage of pore space is greater by
volume) and thus less wicking.

Texture
  Grain morphology and appearance:  Silica-rich nodular coating on ash. Ash is
sub-angular to angular and black to rust-red. Opal is concentrated on edges of
clasts and appears white in high concentrations and as a clear, vitreous
coating in lower concentrations. Hemispheric silica-rich deposits are about 1
mm.
  Grain size and sorting:  Ash clasts are about 1 mm in diameter on average,
though approximately 10% are smaller clasts.
  Grain fabric:  Random orientation.

Sediment structure:  None.

Color: Black to rust-red ash mixed with whitish opaline grains.