Light sensitive crystals
If you own or plan to collect crystals, it’s essential to know which ones are sensitive to light or moisture. Prolonged exposure to sunlight or high humidity can cause some crystals to fade, darken, or even break. Protect these delicate stones by storing them in a dark, dry place.
Crystals That Fade, Darken, or Break Under Sunlight
| Crystal | Reaction | Crystal | Reaction |
|---|---|---|---|
| Amethyst | Very slowly fades due to IR and heat. | Creedite | Purple creedites are extremely light sensitive. |
| Amazonite | Fades slowly over time. | Crocoite | Darkens quickly. |
| Anglesite | Brown shades fade. | Cuprite | Darkens slowly, copper is liberated. |
| Anhydrite | Blue hues fade with light exposure. | Diamond | Yellow diamonds may turn green; red diamonds fade to pink. |
| Apatite | Pink fades quickly under sunlight. | Djurelite | Fades, especially Irish specimens. |
| Aquamarine | Natural colors are stable, but irradiated colors fade. | Dolomite | Pink fades with light exposure. |
| Aragonite | All colors fade in sunlight. | Fayalite | Green changes to blue. |
| Argentite | Gradually fades over time. | Fluorite | Colors may fade depending on origin. |
| Aurivilliusite | Fades quickly under sunlight. | Hackmanite | Colors can shift from red to green, blue, or colorless. |
| Barite | Colors such as blue, yellow, or brown may change or darken. | Halite | Blue or yellow hues may change under light. |
| Brazilianite | Fades slowly with light exposure. | Haüyne | Blue pales gradually. |
| Bromargyrite | Darkens as silver is liberated. | Hisingerite | Turns from red to brown. |
| Celestine | Fades slowly under sunlight. | Hiddenite | Fades to pale shades. |
| Chlorargyrite | Shifts from gray to violet-brown as silver is liberated. | Galkhaite | Darkens gradually with light. |
| Cinnabar | Darkens with prolonged exposure. | Ianthinite | Shifts from purple to greenish-yellow. |
| Coquimbite | High humidity accelerates oxidation to yellow crystals (Copiapite). | Inesite | Fades gradually under sunlight. |
| Corderoite | Pink fades quickly, especially from McDermitt Mine specimens. | Kleinite | Yellow fades to orange. |
| Corundum | Yellow shades may fade. | Kunzite | Pink fades, and green fades extremely quickly. |
| Proustite | Darkens very fast under light. | Vivianite | Darkens gradually over time. |
| Spinel | Red darkens slowly under sunlight. | Wulfenite | Red fades with prolonged exposure. |
| Xanthoconite | Fades under light exposure. | Zircon | Brown darkens over time. |
Fluorite
(Pink to colorless; green to purple; blue or purple to colorless or pink)
| Location | Fluorite reaction to Light |
|---|---|
| Bingham, NM | Blue fades with exposure to sunlight. |
| El Hamman, Morocco | Ink blue pales with 30 minutes of direct sunlight exposure. |
| Elmwood | Fluorite is reported to be stable. |
| Haute-Loire, France | Sky blue turns colorless with 30 minutes of direct sunlight. |
| Hilton | Yellow fluorite is reported to be stable. |
| Navidad Mine | Deep grape purple when mined, but miners put it in the sun for 6-9 weeks to turn it pink. |
| Sant Marçal, Montseny, Spain | Deep blue turns dirty green with 1 hour of direct sunlight exposure. |
| Weardale (Cowshill area) | Pale green changed to purple almost immediately on exposure to daylight (not direct sunlight). |
| Weardale (Rogerly, Heights, Cement Quarry, White's Level) | Green fluorite is potentially unstable, though to varying degrees. Purple color appears more stable. Deep green fluorite from Rogerly (Solstice Pocket) permanently changed to muddy gray-green almost instantly under a LWUV lamp; this process took longer in sunlight. |
Quartz
(Most colored quartz is a bit light sensitive)
| Type | Reaction to Light |
|---|---|
| Amethyst | Fades over time. |
| Brazilian Amethyst | Fades with prolonged sun exposure. |
| Nebraska Amethyst | Bleaches after a couple of days in the sun. |
| Citrine | Light sensitive, prone to fading. |
| Morion | Color changes over time. |
| Rose Quartz | Fades gradually under sunlight. |
| Smoky Quartz | Can change from smoky to greenish yellow or colorless. |
| Agate | Prone to fading with prolonged sunlight exposure. |
| Opal | Light sensitive and prone to fading. |
Topaz
(Brown to colorless or blue; blue to paler or colorless)
| Location | Reaction to Light |
|---|---|
| Thomas Range, UT | Most sherry topaz crystals turn colorless with exposure to sunlight. |
| Thomas Range, UT (East Side) | Sherry topaz turns pink after 1-3 weeks in the sun due to pseudobrokite inclusions. The pink is stable after one year. |
| Little Three Mine | Collected as colorless but turned blue upon sun exposure. Blue color appears stable, particularly from the 1976 and 1991 pockets. |
| Villa Garcia, Zacatecas, Mexico | Sherry-colored topaz is reported to have stable color. |
| Mokrusha Mine, Urals | Sherry-colored portions fade and turn light blue under sunlight exposure. |
| Volodarsk/Volhynsk, Ukraine | Dark orange fades quickly under sunlight. Bicolored samples (light pinkish champagne and blue) are reported to be more stable for at least 15 years. |