Andean opal is a lovely bluegreen translucent opal found in the Andes mountains near San Patricio, Peru. Copper may be the essential trace element that causes its soft distinctive color. It has been used by native South Americans for more than a thousand years and is well known in the semi-precious stone trade.
Peruvian blue and pink Andean opal is relatively rare. It is a very translucent stone with color similar to the Caribbean Sea. Depending on how the stone is cut it can be clear, scenic showing varying degrees of color or dendritic which has black fern like inclusions.
- PHYSICAL CHARACTERISTICS:
- Color: is white, colorless, pale yellow, pale red, gray or black, pink, blue, pale green, color of the rainbow.
- Luster: is vitreous to pearly.
- Transparency: Specimens are transparent to translucent.
- Crystal System: Does not apply because opal is amorphous.
Habits: include massive, often stalactitic or rounded forms.
- Botroidal, reniform earthy, nodular and as veins, cavity-fillings such as in fractures and geodes, nodular, reniform or as a replacement of other minerals and wood.
- Cleavage: is absent.
- Fracture: is conchoidal.
- Hardness: is 5.5 -7 on the Mohs scale of hardness.
- Specific Gravity is approximately 2 -2.5 light.
- Streak: is white.
- Other Characteristics: can sometimes fluoresce in various hues of green, or blue purple or white. It demonstrates a rich hue of colour some phosphoresce and all specimens can be very sensitive to impacts and low temperatures. Opal forms the skeletons of some marine organisms, such as diatoms. Diatomite, or diatomaceous earth is a sedimentary rock made up of the remains of diatoms.
- Associated rocks are chert, a form of microcrystalline quartz, volcanic rocks and many others.
- Notable Occurrences Formed by weathering and alteration of siliceous rocks being deposited at low temperatures, especially in the area of geysers and hot springs. So. America, Peru.
- Best Field Indicators are color, low density, fluorescence, fracture filling tendency and lack of cleavage or crystal faces.
Recent commercial production is making more of this expensive material available to jewelers and craftsman around the world.