Hvad er ædelstene optiske fænomener?

Ædelsten optiske fænomener

Gemstones optiske fænomener skyldes den måde, hvorpå lys interagerer med en krystalstruktur af en ædelsten. Denne interaktion eller interferens kan være i form af lysspredning, refleksion, refraktion, diffraktion, absorption eller transmission.

Adularesence

Adularescence is a blue sheen phenomenon reflecting on the domed cabochon surface of Moonstone. The phenomenon of shimmer comes from the interaction of light with layer of little “albite” crystals in moonstones. The thickness of layer of these tiny crystals determine the quality of blue shimmer. Thinner the layer, better the blue flash. This usually appears as a billowy light effect. Moonstone is orthoclase feldspars, another name is “selenite”. Romans called it Astrion.

asterism

Gem cutters vælger ofte at skære cabochon figurer, når sten er lav kvalitet. I sådanne perler og sten, når lyset falder på cabochonoverfladen og danner stjernelignende stråler, kaldes fænomenet asterisme. Der er 4 ray og 6 ray stjerner observeret normalt. Dette sker, når nålens orientering som indeslutninger eller silke inde i krystallen er på mere end en akse.

chatoyancy

From the french name “Chat” mean cat. Chatoyancy refers to a phenomenon akin to opening and shutting of cat’s eye. We can observe in chrysoberyl cat’s eye gem with great clarity. Cat eye gems have a single sharp band, sometimes two or three bands, running across the domed cabochon surface. Cat’s eye gemstones in cabochon shape are cut highlight chatoyancy. The straight needles of the crystal structure of the stone are perpendicular to the phenomena. So when light falls on it, the sharp band can be seen. In the best cases, the chatoyant Chrysoberyl cats eye visually separates the surface into two halves. We can see a milk and honey effect when the stone move under light.

iridescence

Iridescens er også kendt som goniochromism, et fænomen, hvor overfladen af ​​et materiale viser flere farver som synsvinklen ændres. Det kan nemt ses i en dues hals, sæbebobler, en sommerfugles vinger, perlemor osv. Uregelmæssigheden af ​​overfladen og de store interstitiale rum tillader lys at passere og reflektere tilbage fra flere overflader (diffraktion), der forårsager flerfarvet visuel effekt. Kombineret med interferens er resultatet dramatisk. Naturperler viser iridescens, der er meget forskellig fra sin kropsfarve. Tahitianperler viser stor iridescens.

Afspilning af farve

The wonderful gem called opal displays a beautiful color. The fire opals from Lightening Ridge, Australia (showing shifting patches of luminous spectral colors against black) are famous for this phenomenon. While this play of color is a type of iridescence, almost all gemstone dealers call it wrongly “fire”. Fire is a gemological term, It’s the dispersion of the light reflect in gemstones. It’s typically visible in a diamond. It is a simple dispersion of light. In case of opals it isn’t dispersion and hence, it’s wrond to use the word “fire”.

Farveændring

The best example of color change is alexandrite. These gems and stones appear very different in incandescent light compared to natural day light. This is largely due to the gems chemical composition as well as strong selective absorption. The alexandrite appears green in daylight and also appears red in incandescent light. Sapphire, also tourmaline, alexandrite and other stones can aslo show a color change.

Labradorescence

Labradorescens er en slags iridescens, men er meget retningsbestemt på grund af krystal twinning. Vi kan finde den i labradorit ædelsten.

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