字幕列表 影片播放 列印英文字幕 [ intro ] Diamonds are iconic and often depicted as shiny colorless stones. But it turns out diamonds are not always like that! Sometimes, diamonds are green. And stranger still, some of them get that way because of radiation. ~ A diamond is just a particular arrangement of carbon atoms. That arrangement is a regular, repeating pattern called lattice. But when the lattice gets disrupted, diamonds can become different colors. The origin of this strange phenomenon often begins underground. Diamonds sometimes form next to naturally occurring radioactive ores like ones that contain uranium or thorium. Radioactive elements like these have an unstable nucleus at the heart of their atoms. Over time they tend to decay into more stable elements and release energy we call ionizing radiation in the process. As these particles are released, they can reach the lattice structure of the nearby diamond and collide with one of its atoms. And if they have enough energy, they can knock a whole atom out of place! The knockout atom then gets jammed between other atoms in the lattice, creating a defect in the perfect carbon pattern. So, you end up with a spot where there should be a carbon atom, but there isn't one. Misplacing a few carbon atoms here or there sounds like no big deal but, it turns out they make all the difference when light bounces inside the crystal. Diamonds are carefully cut so when light enters, it gets reflected inside in just the right way for the light to escape back out, giving it its sparkly white appearance. But when the diamond has a defect the story is a little different. The light gets absorbed by atoms around the lattice gap, and sometimes in combination with other defects, instead of just being reflected. That's because those nearby atoms aren't as tightly bound by the structure of the lattice as they used to be. So they can move around a little bit and absorb the energy from light waves as kinetic energy. In particular, defects tend to absorb the red and blue parts of the visible spectrum. Without red or blue light, the remaining light that gets reflected out of the diamond contains proportionally more green light, making them look green on the surface! ~ Less than one in every thousand diamonds takes on the striking green color caused by natural radiation, making them super rare. And among green diamonds, some extra rare ones aren't green only on the surface; the whole diamond is green! A great example is the famous Dresden Green formed with natural radiation. Why their whole body is green is still debated, but it might come down to specific geological conditions and radiation sources. With a little inspiration from nature, scientists have found ways of making diamonds green in the lab. Since the middle of the twentieth century, laboratories have used artificial radiation sources like electron beams, to turn ordinary diamonds into green ones. This might be a little alarming because some green diamonds might be radioactive, which might seem a little dangerous. But in the US, the process of irradiating gemstones this way is tightly regulated. So that even if the diamonds become radioactive themselves, they're held in safe storage until their radioactivity drops to a safe level. So, if you have the good luck of receiving a green diamond, you can rest easy that it won't do any harm to you if you wear it. Except, maybe, making your friends green with envy. Thanks for watching this episode of SciShow! We've made thousands of educational videos over the years, and we've been able to offer them for free because of our patrons on Patreon. So, to all of our patrons, thank you for what you do to make SciShow happen. If you're not a patron but want to learn more about what that means, you can go to Patreon.com/SciShow.