The beautiful iridescent patterns of hematites are actually a form of tarnishing.
Hematite is a reddish-brown metallic mineral with chemical formula Fe2O3. Some examples of hematite are renowned for exhibiting strikingly beautiful iridescence--when an apparently monochromatic surface produces a whole rainbow of colors depending on viewing angle. As the iridescence of hematite varies greatly, your best option for owning iridescent hematite is generally to procure a sample that is naturally iridescent--such as rainbow hematite--rather than attempt to force iridescence in a stone that is not naturally inclined to it. Nevertheless, iridescence is a form of tarnish, so you can take steps to bring out the maximum potential iridescence of your sample.
Instructions
1. Apply a thin coating of liver of sulfur to your hematite. Liver of sulfur is a sulfurous solution used to induce tarnishing in metals. It can be found in most art supply stores, often marketed as a brass duller.
2. Place the hematite in a plastic bag and seal. The oxidization reactions at work in many types of tarnishing require sulfur as a catalyst. Liver of sulfur enables tarnishing to proceed at a much faster rate than it normally would by providing a sulfurous environment favorable for tarnishing.
3. Leave the hematite to sit in a warm location for 24 hours.
4. Remove the hematite from the bag. Gently wipe the liver of sulfur off the hematite, taking care not to wipe off any iridescent tarnish that may have formed underneath.
5. Hold your hematite under a light. If your species is capable of iridescence, it should now appear.
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