color changing circle

Sphene or Titanite changes color from green to red.

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The color-changing ball, or titanite, is a calcium non-silicate mineral called CaTiSiO5. Trace amounts of iron and aluminum impurities are usually present. Rare earth metals are common, including cerium and yttrium. Thorium partially replaces calcium with thorium.

Titanite

Sphene occurs as translucent to transparent red-brown, as well as gray, yellow, green or red monoclinic crystals. These crystals are usually related and often doubled. Possessing subadamantine, having a slightly resinous luster, titanite has a hardness of 5.5 and a weak cut. Its density depends on 3.52 and 3.54.

The refractive index of titanite is from 1.885-1.990 to 1.915-2.050 with strong birefringence from 0.105 to 0.135, biaxially positive, under the microscope this leads to a characteristic large relief, which, in combination with the usual yellow-brown color, as well as a diamond-shaped cross section, facilitates the identification of the mineral.

Transparent specimens are distinguished by strong trichroism, and the three colors shown depend on the color of the body. Due to the quenching effect of iron, the stone does not fluoresce in ultraviolet light.

Some of the titanite was found to be metamictite as a result of structural damage due to radioactive decay of the often significant thorium content. When viewed in thin section with a petrographic microscope, we can observe pleochorism in the minerals surrounding the titanite crystal.

Spen is a source of titanium dioxide TiO2 used in pigments.

As a gemstone, titanite is usually a shade of grey, but can be brown or black. The hue depends on the Fe content: low Fe content produces green and yellow hues, while high Fe content produces brown or black hues.

Zoning is typical for titanites. Valued for its exceptional dispersion power of 0.051 in the B to G range, surpassing diamond. Spen jewelry is rare, the gemstone is of rare quality and relatively soft.

Color change

A good example of color change is sphene. These gems and stones look completely different under incandescent light than they do in natural daylight. This is largely due to the chemical composition of the stones and the strong selective absorption.

Sphene appears green in daylight and red in incandescent light. Sapphire, as well as tourmaline, alexandrite and other stones, can also change color.

Color change video

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