HALITE SALT CASTS
One of the most distinctive and environmentally
diagnostic (& rare, in my experience) features in the sedimentary record is
a halite salt cast.
Halite (NaCl - sodium chloride) is a relatively common
mineral - it is abundantly preserved in ancient evaporite successions and
modern evaporite settings. If seawater-soaked siliciclastic sediments dry
out, halite crystals may form. Halite crystals will almost always have
nice cubic forms, but they can have embayed faces. This mineral is
readily soluble in water, so halite may precipitate and redissolve relatively
quickly. The crystal forms may become preserved in the sediments,
as casts. Preserved halite salt casts unquestionably demonstrate that the
sedimentary environment was an evaporite setting.
Halite salt casts (field of view ~3.5 cm across) in friable mudshale
from the Twist Gulch Formation (Middle Jurassic) of central Utah, USA.
Locality:
loose piece from near small abandoned copper mine at Twist Gulch
Formation-Flagstaff Limestone angular unconformity outcrop in Salina Canyon,
central Utah, USA.
Collected & generously donated by Lee St. John
& Mary Ellen St. John.
Halite salt casts (field of view ~17.7 cm across) in reddish silty
mudshale from the Twist Gulch Formation (Middle Jurassic) of central Utah, USA.
Locality:
loose piece from near small abandoned copper mine at Twist Gulch
Formation-Flagstaff Limestone angular unconformity outcrop in Salina Canyon,
central Utah, USA.
Specimen owned by Matthew Buxton.
Halite salt casts (above & below) (close-ups of specimen shown
above) in reddish silty mudshale from the Twist Gulch Formation (Middle
Jurassic) of central Utah, USA.
