What is the difference between green turquoise and turquoise (blue) turquoise? I have some of both and I also think some of my pieces have changed color.
Turquoise comes in all shades of blue, to blue-green, with a possible shading towards brown-veined greens.
Matrix (veining) may or may not be present in any color(s). It is the natural variations in turquoise that make it appealing.
The color of turquoise in American Indian jewelry ranges from brownish green to bright blue.
Found in veins sandwiched in between layers of mother rock, the turquoise can show some of the influence of the mother rock in its matrix or veining. The matrix colors range from blue to golden brown to black and sometimes with golden flecks (sometimes called “fools gold” or iron pyrite), which is considered very desirable by some.
The more blue, the higher the copper content. The more green, the higher the iron content.
Turquoise can change color over time due to exposure to oils from the skin, lotions and any other oily liquids that the stone comes in contact with. Blue turquoise tends to turn green after 10, 20 or 30 years. But not all blue turquoise will turn green. Why?
High quality turquoise is so dense that it is not porous enough to allow oils to invade and change its color. Very high quality turquoise does not need to be stabilized or protected – it can be used in its natural form.
Lesser quality turquoise is often porous so needs to be stabilized to protect it from the wearer and the environment.
Because most old turquoise was not treated, it seems to eventually turn green. A vintage piece with patina on the sterling silver and green stones go together like milk and cookies.
Some contemporary artists capitalize on that and when they produce an antiqued piece they choose for it a turquoise stone from one of the mines that produce green stones.