SPIDER WEB TURQUOISE: Spider web is made up of small nuggets cemented together with natural rock or matrix. When cut through, the aggregate mass of nuggets resembles spider web. Most mines produce some spider web turquoise.

SEA FOAM TURQUOISE: Sea Foam is a descriptive term recently applied to a kind of knobby, foam-looking nugget that can be polished without cutting, except for flattening the back to mount in jewelry. Many mines have produced this type of nugget, but it has not been popular until the new term “Sea Foam” appealed to the buyer.

TURQUOISE QUARTZ: Turquoise, like most gemstones, can occur deeply embedded in a quartz matrix, often very sparkly and beautiful. Bisbee is a mine that often produces turquoise quartz, or druzy turquoise. The turquoise below is from Gilbert Mines.

MINERAL TURQUOISE:

Chemical composition: CuAl6(PO4)4(OH)8*5(H2O)
Hydrated copper aluminum phosphate.
Class: Phosphates
Color: Blue, green, blue-green.
Luster: dull to waxy
Transparency: opaque
Hardness: 5-6.
Refractive index: 1.62
Crystal structure: Triclinic(massive)
Crystal Habits: crystals are rarely large enough to see,
usually massive, cryptocrystalline forms Such as nodules
Cleavage: perfect in two direction, but not often seen
Fracture: conchoidal and smooth
Specific Gravity: 2.6-2.9
Streak: white with a greenish tint
Sources: Iran (Persia), Tibet, China, Egypt,
Arizona and Southwestern United States
Associated Minerals: pyrite. limonite. quartz and clays

What are the different “kinds” or grades of turquoise?

1. NATURAL turquoise means a stone with no alteration to its composition. Such stones are merely polished and cut into shapes before being mounted in jewelry. Natural turquoise remains porous, as all natural stone is to varying degrees, and may tend to change color over time as it is worn and handled. A+ grade or higher.

2. STABILIZED turquoise means that the natural mineral has been chemically altered to harden the stone, usually by infusing epoxy or polystyrene into the porous surface of the stone. The stabilization process serves to “freeze” the color of the stone so it will not change. Sometimes A+ grade, but usually A to B grades.

3. COLOR-TREATED, color-enhanced, or color-infused turquoise means that the natural mineral, usually too soft and pale to finish for use in jewelry, has been chemically altered to change the color of the stone (and often the hardness also). Dye is mixed with a stabilizing epoxy or polystyrene liquid and infused into the stone under pressure. Turquoise Obsession does not sell this type of stone. B grade stones.

4. RECONSTITUTED turquoise is the name used for turquoise dust and chips that are mixed with plastic resins and compressed into a solid form so as to resemble natural turquoise. Turquoise Obsession does not sell this type of stone. C to F grade stones.

5. IMITATION or SIMULATED turquoise is any laboratory created synthetic compound (usually dyed plastic) which is manufactured to resemble turquoise, but which contains no actual gemstone. Turquoise Obsession does not sell this type of stone. Not a real turquoise.

How Does Turquoise Form in Nature?

Chemically, a hydrated phosphate of copper and aluminum. Turquoise is usually found in the”alteration zones,” of arid or desert regions. These zones are areas where the native, original rocks have been altered through the intrusion of other rocks from some volcanic or other thermal influence. The hydrothermal alteration is created by magma solutions from deep in the earth being forced to the surface through fractures or pores which eventually change the original rocks.

Several steps and processes are necessary to create turquoise. First there must be a source of copper. This occurs in a rather limited number of areas in the world. There must be a source of phosphorus CO-located with the copper. Usually from the mineral, Apatite. Which is not always in rocks associated with copper.

There must also be feldspar for the aluminum. Along with deep hydrothermal alteration. Which breaks down the feldspars and frees the aluminum needed for the turquoise. The phosphorus usually comes from phosphoric acid leached from the Apatite, during the hydrothermal alteration.

The copper is usually introduced into the “host” rocks by the rising hot magma. The copper readily oxidizes near the surface when it is in the hot magma solution. It reacts freely with the aluminum and phosphoric acid to form turquoise.

At this time other minerals enter into the turquoise structure and create color variations. The chemical formula of turquoise is: (CuAl6 (PO4)8 4H2O) this structure will very greatly with the introduction of Iron, Calcium, Magnesium, Manganese, Silicon, and Zinc. These additional elements when incorporated in the molecular structure of turquoise influence its color and hardness. The color of turquoise can vary from a deep blue to a deep green, with every variation of color in-between.

Generally, the more copper in the molecular structure the bluer the turquoise. The introduction of iron causes the greener cast to the stone. Turquoise creation is affected by many other factors too. For example; the best, hardest turquoise is found within 100 feet of the earth’s surface

This is not to say that turquoise has not been found in areas without igneous or volcanic activity. Turquoise has been found in the Sinai and in Australia. In these two areas it is found in sandstone and shale.

Its One other key geological activity is called silicification. It too is an act of hydrothermal and intrusive alteration. Here silica, which is a common associate of turquoise, is introduced into the turquoise deposit. This addition and periods of intense heat are responsible for the hardness of the turquoise and frequently the matrix as well.

Physical Properties of Turquoise

Turquoise is opaque and has a Mohs scale hardness that varies greatly. The deeply mined chalk like turquoise may only have a mohs hardness slightly over 2. Where as a gem specimen mined closer to the surface may be up to 6. The hardness varies due to several factors. Environment and matrix are key. In silica verities quartz particles are present and the stone will be hard enough for use as a gem stone. Silicification will strengthen some of the matrix as well.

If silicification has not occurred the turquoise will likely be chalky, porous, and soft. It will not be usable in jewelry without undergoing treatment. Usually stabilization. Stabilization may also be used because moisture will cause turquoise to turn toward green This can occur in the ground or in jewelry by absorbing moisture and oils. This is not unlike blue azurite changing to green malachite as its creation environment increases its water content.

Turquoise must consist of copper, aluminum and phosphorus. Other elements can replace various percentages of these and change the molecular structure. For example, two very rare minerals, chalcosiderite (where iron replaces the aluminum) and faustite (where zinc replaces the aluminum) do exist in turquoise environments. Usually there will only be a partial replacement of the aluminum with iron and zinc, thus leaving the turquoise altered only in color.