This is a natural
occurrence of
Mirabilite crystals growing in contact with a saline spring in Camp Verde,
Arizona. The Mirabilite crystals have lost much of their water and are
turning to a white powder. Both long prismatic crystals as well as short
prismatic (tabular) crystals are shown in the photo. See other pictures of
Mirabilite below the list of physical properties.
CHEMISTRY NaSO4 .10H2O
CRYSTALLOGRAPHY Monoclinic
CRYSTAL GROWTH AND HABITS Mirabilite is prismatic, commonly acicular and also tabular or lath like. It may be massive or as crusts, granular or stalactitic.
COLOR AND OTHER OPTICAL PROPERTIES Colorless to dull and white
HARDNESS 1.5 - 2
SPECIFIC GRAVITY 1.5
LUSTER Vitreous to dull
STREAK White
BREAKABILITY Perfect cleavage in one direction, conchoidal fracture, brittle
OCCURRENCE Mirabilite is found near saline springs and along saline playa lakes.
ASSOCIATED MINERALS Gypsum, Halite, Thenardite, Trona, Glauberite, Epsomite
OTHER PROPERTIES Mirabilite has a saline and bitter taste. It dissolves readily in water and quickly looses its water in air and turns to a white powder (NaSO4 - Glauber's Salt).
The following pictures are of Mirabilite crystals that were grown in a fish tank (10 gallon) in my driveway. After returning from a collecting trip to Trona, California I place a few Hanksite crystals in fresh water. They dissolved in the fresh water and precipitated Mirabilite crystals. These crystals were harvested on successive early mornings.
This is a before and after picture of Mirabilite. This divergent cluster of crystals is about 8 inches high. The dark coloration on the bottom left picture is what is left of one of the Hanksite crystals (after solution in the water). The picture on the left was taken only minutes after being pulled from the brine in the fish tank. The picture on the right represents 24 hours of dehydration in the dry air of Arizona.
A closer
view of the above picture.
This is another before and after picture. This was one of the best "single" crystals collected from the tank. It is about 2 inches long. It nicely shows the tabular or lath like growth form along with many parallel growth lines.
This is the same crystal from above, but now completely dried. The crystal structure is very skeletal and easily crumbles as shown on the right.
This picture
shows the 10 gallon fish tank from which the Mirabilite crystals grew. A
small piece of wood was placed on the surface of the water. During the
evening these crystals grew. The wood was still floating on the brine
(even with all of these crystals attached) when
it was removed, flipped over and placed on the top of the tank for this picture.