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Thenardite
Na2SO4 orthorhombic
Thenardite is a water soluble evaporate mineral and unless care is taken to keep these in a cool dry place, they will end up as piles of white powder in your storage boxes. Most of the localities where these specimens occur they can be found in great abundance and can be harvested hear after year and would be if the market could absorb them.
[Rock Currier 2009]
Thenardite
Chile
Tarapacá Region
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These attractive specimens did not form in the borate deposit at Boron, but rather in the settling ponds west of the refinery which is also situated west of the open pit mine that has produced almost all the specimens that have made this deposit familiar to collectors. At one time it was the largest underground operation in California with more than 200 miles of workings but the advent of large earth moving equipment made it more economical to mine the deposit as an open pit operation, though some day when the pit gets deep enough, mining may again shift to an underground operation if that will make it more profitable. When the ore is mined, and almost all the ore that is currently being exploited is crystalline Borax, it is crushed and run into big million gallon plus dissolving tanks. In these tanks it is mixed with hot water and large rotating mixing blades stir the borax till it is dissolved and the mud and impurities in the ore drops to the bottom of the tanks. Eventually this mud is pumped out into big shallow settling ponds where the mud settles out. Sometimes when the conditions are right in these ponds, especially in the early morning when the temperature is low, beautiful big crystals of mirabilite grow in the water where they can be harvested by interested parties. This does not mean the general public, because this is a big industrial operation and access to the mine and refinery areas is strictly controlled. These specimens were collected by Jim Minette who for years worked for US Borax as a mining engineer and eventually became general manager of the mining operation there. He would sometimes go out early in the morning to settling ponds and collect these specimens and lay them out on the bank to dry which didn't take very long. They Mirabilite would loose its water and convert to Thenardite. They had to be handled with great care because they were very delicate. He would take them home and spray them with Krylon plastic to preserve them.
[Rock Currier 2009]
Thenardite
USA
California, San Luis Obispo Co. Carrizo Plain, Soda Lake.
Soda lake, a bit east of Taft, California is probably home to most of the thenardite specimens that have reached the mineral market during the last 30 years. They are typically clusters of diamond shaped crystals, but gray and unless kept in a cool dry environment have a nasty habit of ending up as piles of white crumbs in your collection, but I have some I collected twenty years ago that are still in good shape. These can still be collected today but collecting is best toward the end of hot dry summers when maximum evaporation has taken place on the lake bed. The lake is really a dry lake bed covered by salt, mostly halite and is many acres in extent and is thought to be a slump feature created by the great San Andreas fault that runs just to the west of the lake. The lake is seasonal and in late summer any water is usually long gone and one is presented with a flat pan of salt which on closer inspection consists of polygonal blocks of salt separated from each other by ridges of rough salt raised an inch or two above the smooth center of the polygons. To collect you walk out onto the surface of the lake perhaps 50 or 100 meters and pick a nice big polygon and break a hole down through the salt crust that is perhaps 20 cm thick to the mud below in which the thenardite crystals commonly grow. The margins of the lake are usually quite muddy and you can easily sink up to your hips in the mud unless you are careful in getting across this and onto the firmer salt. Some people lay down a piece of old plywood or some wooden planks. Some make up crude “snow shoes” like nailing an old pair of sneakers to pieces of wood. This distributes your weight evenly on the surface and keeps you from sinking in. Once you have broken through down into the mud layer you reach down into the mud with you hands and feel around for the crystals. You have to feel carefully because they can be quite sharp. You pull them out of the mud, rinse the mud off with the brine and lay them at the side of the hole and dive back in for more. You get single crystals and clusters, some of them so large you have to break them up a little to get them out of the hole. As the hole gets larger, the crust of the polygon starts to break up and you start to sink down a little. It helps if you take along a piece of plywood to lie on, but ultimately you get more and more of the often fowl smelling mud on you and pretty soon you are pretty well covered with the stuff. Pretty soon you just don’t care any more and late in the day if one of your collecting buddies has a nice clean spot, say on the back of his shirt, you are more likely than not to help him cover that spot with mud as well whether he wants you to or not. If you are lucky you may find some blödite crystals, though I was only able to find this elusive mineral one time and that was quite deep in the mud. Sometimes you pull fabulous crystal clusters of mirabilite from the mud as well and at least for a few minuites you think you have struck the mother load till they start to wilt and turn white and in the space of an hour or two turn into a pile of white crumbles on the side of your hole. See the
article on mirabilite if you want to see what a good unaltered mirabilite looks like.
When you collect at this locality you really need to take along an extra set of clothing and about five gallons of water with which to wash off the mud when you finish collecting. I made the mistake first time around of not doing this, and it took me a week to wash out most of the mud. I used the last of my drinking water to wash the caked salt off of my arms. The caked salt also sort of welded all the hair on my arms together which gave one quite a strange sensation when you brushed up against something. Wow! That felt pretty strange. After you have removed your pants, they frequently will stand up on their own because of the caked salt and mud in them. This is one of the dirtiest collecting localities that I have ever experienced.
[Rock Currier 2009]
Rock Currier
Crystals not pistols.
Edited 9 time(s). Last edit at 09/06/2009 03:55AM by Rock Currier.
