eli5 What determines whether a gem is a sapphire, ruby, emerald, diamond, etc if those gems don’t necessarily have to be the most common thought color? For example, sapphires can be colors other than blue. What’s the difference between a red sapphire and a ruby?
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The simplest answer is that the common gem names are applied to whatever people agree to call them. The distinction between a ruby and a sapphire is entirely arbitrary. Why is red corundum called a ruby? Because ruby meant red. Emerald meant a green gem and has been applied to malachite at times. Sapphire May have come from it being sacred to (what would be called) Saturn, probably wasn’t what the Greeks called sapphires, but instead was because they described sapphires as blue. Diamond was called such because it was super hard. All of those gem names came from either observable phenomena or cultural legacies. Not scientific consistency.
Our definitions of what constitutes a ruby ultimately comes down to organizing what different people called recurring groups of minerals. We could get rid of ruby entirely because it’s uniqueness comes from its color and that the name is popular. We could call it a red sapphire and it would probably be more accurate.
Gemstones are usually different minerals (although some organic materials are worn as gems in jewelry like pearls and amber) and most of them get their color from structural or chemical impurities that refract light in different parts of the spectrum.
Interestingly enough there’s a pretty large variety of quartz that would include rose quartz, amethyst, citrine, ametrine, jasper, and agate but aside from color I’m not entirely sure what would make those quartz varieties distinct.
Fun fact though: peridots are always green.
The simplest answer is that the common gem names are applied to whatever people agree to call them. The distinction between a ruby and a sapphire is entirely arbitrary. Why is red corundum called a ruby? Because ruby meant red. Emerald meant a green gem and has been applied to malachite at times. Sapphire May have come from it being sacred to (what would be called) Saturn, probably wasn’t what the Greeks called sapphires, but instead was because they described sapphires as blue. Diamond was called such because it was super hard. All of those gem names came from either observable phenomena or cultural legacies. Not scientific consistency.
Our definitions of what constitutes a ruby ultimately comes down to organizing what different people called recurring groups of minerals. We could get rid of ruby entirely because it’s uniqueness comes from its color and that the name is popular. We could call it a red sapphire and it would probably be more accurate.
Gemstones are usually different minerals (although some organic materials are worn as gems in jewelry like pearls and amber) and most of them get their color from structural or chemical impurities that refract light in different parts of the spectrum.
Interestingly enough there’s a pretty large variety of quartz that would include rose quartz, amethyst, citrine, ametrine, jasper, and agate but aside from color I’m not entirely sure what would make those quartz varieties distinct.
Fun fact though: peridots are always green.
The impurities are what give gemstones their different colors.
Gems have crystalline structures, meaning the atoms appear in a regular, 3D pattern. For instance, aluminum oxide is made of aluminum and oxygen. But if you replace a tiny fraction (around 1% or less) of the aluminum with something else – like iron, titanium, vanadium, chromium, or various other metals – you can get different colors.
In the periodic table, these transition metals produce colors when they oxidize (chemical name for “rust”). You already know that iron becomes orange when it oxidizes. Chromium can be yellow or purple. Titanium can be pink or blue. Chromium can be red. And so on…
Different combinations of metals in different concentrations create a wide variety of colors in these crystals.
The impurities are what give gemstones their different colors.
Gems have crystalline structures, meaning the atoms appear in a regular, 3D pattern. For instance, aluminum oxide is made of aluminum and oxygen. But if you replace a tiny fraction (around 1% or less) of the aluminum with something else – like iron, titanium, vanadium, chromium, or various other metals – you can get different colors.
In the periodic table, these transition metals produce colors when they oxidize (chemical name for “rust”). You already know that iron becomes orange when it oxidizes. Chromium can be yellow or purple. Titanium can be pink or blue. Chromium can be red. And so on…
Different combinations of metals in different concentrations create a wide variety of colors in these crystals.
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