This stunning specimen of malachite resembles a marine boulder encrusted with greenery, which can almost be seen to undulate in a gentle marine current. The fronds are pseudomorphs, the replacement of one mineral in its original crystal shape by another, in this case azurite (another copper carbonate mineral). The green bubbles are secondary malachite, showing a habit called botryoidal.
The specimen is from Brazil, and measures 10x8x5 Cm.
It is prepared by precipitating copper(II) hydroxidefrom an aqueous solution of copper sulfate or copper carbonate using sodium hydroxide or ammonia, then dissolving the precipitate in a solution of ammonia.
It forms a deep azure solution. If the solution is evaporated, it leaves light blue precipitate of copper hydroxide.
If the solution is evaporated, it leaves light blue precipitate of copper hydroxide. This is because the formation of the tetraminocupric complex is reversible and ammonia evaporates together with the water. If the evaporation is conducted under stream of ammonia, then deep blue needle-like crystals are formed.
Schweizer’s reagent finds use in production of cellulose products such as rayon and cellophane, because wood pulp, cotton fiber, and other natural cellulose sources are soluble in the solution. Dissolved cellulose precipitates when the solution is acidified. (x)
Today, my brother and I received distress signals coming from the Atlantic Ocean. We quickly sailed the Stan O’ War II over to the location of the signals and what we saw was something… otherworldly. To say the least.
An enormous skyscraper of an anomaly arose from the ocean floor and nearly took us out in one hit with its intense water-kinesis abilities. The thing had what appeared to be a gemstone for a nose, multiple limbs, and four eyes. The strange markings on its blue-green skin resembled that of a Malachite - a copper carbonate hydroxide mineral!
Was this creature some sort of gem monster from another world? Or simply a hyper-evolved gemstone that hybridized with a different anomaly entirely? It isn’t clear to me, and truthfully, we didn’t really stick around long enough to find out!
So, as promised Ill be posting some glaze recipes. This cup was one of my more popular posts so I figured it would be a good one to start with.
This cup was fired in a soda kiln, the blue comes out when the soda interacts with the glaze, and the red specks only occur when fired in heavy reduction. because of this, I tend to fire this glaze with shinos, as they both benefit from reduction. However, the copper content of this glaze causes fuming, and often affects the glazes around it.
We recently shared (see http://on.fb.me/1Ot7Ms1) a piece of mine timber from an old copper mine in Arizona that was partially replaced by the copper carbonate azurite, precipitated from the waters percolating through the metal rich mine. In this sample, from the antique copper mines of Troodos in Cyprus that fuelled the Bronze Age around the Mediterranean (see http://on.fb.me/1Oleeph), a slice of trunk has been infiltrated by copper rich waters, and the pure native metal has precipitated within its grain, each zone surrounded by a faint green area tinged with copper oxides.
I’ve created a colorful set of solutions mostly from mineral samples in the geology lab. From left to right, we have:
CoCl2 was obtained by stealing some from the chemistry stockroom. I initially tried to get a pink solution of MnCl2 by dissolving rhodochrosite (manganese carbonate) in hot HCl, but that didn’t work very well…
FeCl2 was created by crushing siderite (iron carbonate) and dissolving it in HCl. The reaction was relatively slow, but works at room temperature.
[CuCl4]2- was created by adding excess NaCl (which is the mineral halite) to a CuCl2 solution. Extra chloride forms a coordination complex with the copper (II) ion, resulting in a green solution.
CuCl2 was created by dissolving malachite (copper carbonate*) in HCl.
CuSO4 was created by dissolving chalcanthite (copper sulfate) into water. It should be roughly the same color as the CuCl2 solution, but the sample here is just more dilute.
BaCl2 was created by dissolving witherite (barium carbonate) in HCl. The reaction was very fast, comparable to that of dissolving calcite (calcium carbonate).
*Malachite contains some hydroxide, so it is actually a copper carbonate hydroxide: Cu2CO3(OH)2
A lovely spray of blue copper carbonate crystallised in what is now the mined out source of Touissit in Morocco. Crystals like these are called ‘floaters’ because they formed in a pocket without contact with the rock walls when carbonate rich water altered a primary copper deposit made of sulphides. The piece measures 5.0 x 3.5 x 1.5 cm.