Mineralogist Answers Gemstone Questions From Twitter | Tech Support

I'm Gabriela Farfan, curator of gems

and minerals at the Smithsonian.

Let's answer some questions from the internet.

This is Gem Support.

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@Okoepp asks, I have a really dumb question

that I'm too scared to ask in class.

What's the difference between rocks and minerals?

There's nothing in a rock that is not a mineral.

Rocks are actually made up of minerals.

This is called granite.

If you look closely at this rock,

you'll notice that it has grains of different colors.

These are individual crystals of different minerals.

Contained in this granite, are the mineral quartz,

the mineral feldspar, and the mineral biotite

and muscovite, which is also known as mica.

All minerals are crystals by definition.

In this case, this mineral is called quartz.

What is a gem?

A gemstone is a mineral crystal that has been cut

and faceted by an artist, so this would be the natural shape

of a crystal, and it can eventually be cut

and polished into a gemstone.

@JebBlackwater asks, Question, what's the difference

between rubies, emeralds, sapphires, et cetera?

Rubies and sapphires are the same exact mineral.

The mineral is called corundum,

and it is made up of aluminum and oxygen.

The only difference between ruby and Sapphire is

that the gem industry designated the color red for rubies.

Every other color of the rainbow is called sapphire.

You also asked about emeralds.

Emerald is a variety of the mineral barrel.

Many minerals get their colors

from different trace element impurities.

This one has chromium 3+ impurities

on a very traced scale,

and this one has iron impurities to make it blue.

@SeamsterHeidi asks,

What's the most unusual gemstone you've ever heard of?

I need some inspiration.

I have a treat for you.

This is a mineral sodalite.

The variety name is called Hackmanite,

and Hackmanites are very special

because they have a color property called tenebrescence,

which happens when we shine a UV light on it.

You'll see that the stones are now glowing

in orange-yellow color,

and we're gonna charge them up a little bit.

Orange stone is from Mont St. Hilaire,

a very famous mine in Quebec,

and the yellow stone is from Afghanistan.

Okay, let's get the lights back on.

Now look at how the color of these stones has changed.

A tiny bit of sulfur gives it this color effect.

And now, if we add some light to them, they'll go back

to their original colorless versions,

so just reflecting all of the light back to us.

@LiPerezRey asks, Where does The Rock Dwayne Johnson rate

on the Mohs Scale?

Well, Dwayne The Rock Johnson is off the scale

because he's a cool human,

but his bones are actually made of Bio Appetite,

which is a mineral with a Mohs Hardness of five.

The Mohs Hardness Scale is a scale that we use

to compare mineral hardness.

So when I say hardness, I'm actually referring

to the scratch ability of a mineral, not how tough it is.

The mineral talc has a Mohs Hardness scale of one.

At the other extreme

of the Mohs Hardness Scale, diamond is number 10.

The Mohs Hardness Scale is also a Logarithmic Scale,

which means that the difference between one

and two on the scale is 10 times.

So diamond is 10 times 10 times 10 times 10,

and so on times harder than the mineral talc.

The reason why hardness is so important for gemstones

that are used in jewelry is

that something like a diamond is very difficult to scratch.

So if you're wearing it every day in a ring,

it's much less likely to turn dull over time

because it will not build up scratches.

Whereas diamonds are the hardest on the Mohs Hardness Scale,

which means scratch ability.

Jade is the most difficult to break,

so it is the toughest mineral.

@PetePeters21 asks,

If diamonds are the hardest substance in the world,

how do they cut diamonds?

In order to cut a diamond, you need to use other diamonds.

They would have to take a rotating plate that we call a lap

and cover it in diamond powder.

They'll start with a very coarse grit of powder,

and eventually, they get to finer

and finer grits to create the polished effect.

This is called the Kimberly Diamond.

It's over 55 carrots in weight

and it originated from South Africa

and was gifted to the Smithsonian in 2019.

This would be a rectangular or emerald cut.

You may also refer to it as a baguette cut,

and it's very special

because most diamonds are cut in a round brilliant shape,

which means that it's very good at disguising flaws.

Light comes into the diamond, bounces around the facets,

and comes back out to your eye.

In this case, the light comes in, it bounces a little bit,

but you can see that there are no flaws in this diamond.

@Sakasci asks, How is a diamond's purity graded?

The four Cs, which stands for its color, its clarity,

its cut, and its carrot weight.

There are many gemological institutes

that can actually give your diamond a grade.

They'll look to see if it has any inclusions

or impurities in the diamonds such as another mineral

that's stuck inside of the crystal,

or if it has any other flaws like a crack.

Then they'll look at the color.

When grading colorless diamonds, people tend to prefer

that there not be traces of yellow.

The yellow is due to small amounts

of nitrogen substituting into the carbon structure

of the diamond crystal.

However, if there's a lot of nitrogen in the crystal,

it will turn more of a brilliant-yellow color,

and that's actually considered a good thing.

We call this a fancy-colored diamond.

They'll also look at how much it weighs,

so the carrot weight, which is a fifth of a gram.

They'll also then judge the cut of the stone.

So is it a round brilliant, is it a pear shape?

Is it a marquee's cut, like an eye shape?

A marquee's cut is an interesting cut

that was more popular in the '80s.

@KXNU asks, Do synthetic slash cultured diamonds

also last forever?

Synthetic diamonds are chemically

and crystal graphically speaking the same

as naturally formed diamonds,

so they're also number 10 on the Mohs Hardness Scale.

They all have the same optical properties,

the same thermal properties, and conductivity properties.

They were just not formed through geological processes.

They were formed in a laboratory.

Unfortunately, for all of us, diamonds will not last forever

because diamonds are formed

at very high pressures and temperatures.

So at Earth's surface conditions,

they are not the stable form of carbon.

Graphite is the stable mineral at surface conditions,

so millions of years from now, maybe even longer,

your diamonds will turn into graphite.

@BloodiedRoman asks, Yo,

they made Minecraft Obsidian into a real thing.

Sorry to break it to you, but obsidian was there first.

Here is a piece of obsidian

and obsidian is actually natural volcanic glass,

so it's not a mineral

because it does not have a crystal structure.

This obsidian glass has the same chemical composition

to our granite.

They were magmas that formed underneath the surface

of our planet, but this one ended up nucleating

and growing crystals, whereas this one never had the chance.

Obsidian also has an anthropological connection

because it was used by prehistoric humans

because it breaks very easily

and forms these con coital fractures,

which can be very sharp,

and they were used to make arrowheads

and other knives.

@RocksbyK1 asks, What is the biggest difference

between fool's gold and real gold?

This is real gold.

Gold is a mineral and it has this beautiful golden color.

In contrast, this is called fool's gold.

The proper name is pyrite,

and it's composed of iron sulfide,

so it's not actually gold at all,

but it also has this beautiful golden luster.

But if we hold them side-by-side, you'll see

that they're actually quite different in color.

They both have the same cubic structure

for their crystal structure.

This one just happened to form more euhedral crystals,

more blocky, obvious crystals.

This one on an atomic scale would still be crystalline.

You just can't see the crystals with your naked eye.

@Caiobbadaro asks, Do we theoretically know every mineral

in the universe?

We currently know of over 5,000 mineral species

on our planet today.

As for the whole universe, I cannot say,

but theoretically speaking, we know that the combinations

of different elements in the periodic table could account

for approximately 9,000.

So we still have a ways to go

to keep finding those minerals.

We're gonna need some more mine in the future

to help us look for them.

@BenKing01 asks, Where do the minerals

in your mobile phone come from?

There are approximately 65 elements that are necessary

to make your cell phone run.

Many of them are considered to be rare Earth elements

that oftentimes come in what we call critical minerals.

For example, one

of these minerals would be called spodumene,

and this mineral happens to have a lot of lithium in it,

and lithium is going to be very important

for those lithium-ion batteries.

We mine spodumene from rocks called pegmatites,

and pegmatites are really, really great at concentrating

what we call these incompatible elements.

These are elements that are either too small like lithium

or too big like uranium that they don't like

to fit in your average crystal structures.

Pegmatite deposits occur across the globe,

but they tend to be concentrated in places like Brazil.

We even have some pegmatites here in the United States,

up in Maine, or in California.

@The_Inspirasie asks, What is the most cursed diamond?

Historically, people love the idea of attaching a curse

or a good story to a famous diamond.

And what more famous diamond than the Hope Diamond,

which resides here at our National Museum

of Natural History.

In the early 1900s, the Hope Diamond was bought

and sold many times,

and all of its owners kept losing their money

and having to sell this diamond.

And its last private owner,

Evalyn Walsh McLean had a rather tragic life

that befall her family and herself.

So this idea of the curse just kept building

and building with the Hope Diamond.

But today, when we think about the Hope Diamond,

we actually think of it as a blessing

because it has become the cornerstone

of our National Gem collection.

@PhilBrown62 asks, How do crystals form?

Different minerals require different temperature

or pressure conditions in order

to build their crystals?

They also need some kind of fluid in order

for those necessary ingredients to get to the right place.

Crystals are formed of atoms,

and so, if you have consistent ingredients, in the case

of this amethyst, which is a variety of quartz,

the ingredients would be silicon and oxygen.

The silicon and oxygen atoms will arrange themselves

in a repeating specific pattern.

In this case, it will make a hexagonal crystal system,

and if you keep adding atoms to this tessellation,

you will eventually end up with a crystal that you can see

with the naked eye.

@Lauraopper asks, Are pearls considered to be minerals

since their origin is organic?

Pearls are technically not minerals

because they are formed through organic processes,

and part of the definition of a mineral is that it has

to form inorganically.

However, I'm actually a bio-mineralogist,

so I do study minerals that are formed

through biological processes, and in the case of pearls,

what we're looking at is the mineral orgonite

or calcium carbonate.

So what happens is that the organism, in this case,

a pearl oyster naturally forms this layer of nacre

or mother of pearl inside of its shell,

and if a piece of debris gets stuck inside of its organism

as it's living, it becomes irritated

and it tries to cover that

with the same nacre that we call a pearl.

Another example of a biomineral would be your bones.

You are in fact a bio-mineralizing organism

where your bones are made up of Bio Appetite.

Appetite is calcium phosphate,

and it's also formed through geological processes.

@Bracer788 asks, What does gem mean?

We say that something is gemmy

when someone could potentially cut a gemstone out of it.

For example, this crystal of barrel, also known

as the variety emerald is very beautiful.

It's rather transparent.

This gemstone could potentially be cut out

of a crystal like this because the crystal is gemmy.

In contrast, this crystal is relatively opaque,

which means it would be very difficult

to cut a gemstone out of this crystal.

@EmmaTheresaJ asks,

My friend has a moonstone, parentheses, orthoclase ring

that the jeweler told her she can't get wet.

Is this true?

What's behind that crystal graphically slash geochemically,

or is this a myth?

Moonstone looks something like this.

You can get it wet.

It's not going to be harmed whatsoever.

Now the jeweler might have been confused

with a different thing, which we call opal.

Opals look something like this

and they are also commonly used in jewelry,

but they're not technically minerals.

Opals are mineraloids, which are almost the same

as minerals but they don't have a crystal structure.

Instead, opals are composed of tiny, tiny spheres made out

of silica, and these spheres are packed together.

This means that opals are very porous

and they can easily absorb water.

So if you're going to do your dishes,

maybe take your opal ring off first.

@TiffySniffs asks, How are geodes formed

and why are they so cool?

Well, I agree that geodes are very cool.

If you were to walk around in Utah

and pick up a rock that looks something like this,

break it open, you might find that it's hollow inside

and that it formed a geode.

So geodes form when you have an open cavity,

and this allows crystals to grow inside of the space.

This one is likely filled with the mineral called quartz

or Silicon Dioxide.

This would be your most common geode that you would find.

If you're going to crack open geodes, make sure

that you wear your safety glasses.

Safety first. [chuckles]

@Shelbbylynn11 asks,

Why does turquoise jewelry have to be so expensive?

Because the gemstones that they're made from are quite rare.

It's very difficult, first of all, for the Earth

to create these amazing minerals

and to form examples of them that are going

to be large enough, pretty enough in order for someone

to want to make jewelry out of them.

The next part would be someone has to mine that stone.

So a miner would go to a mine, such as one in Arizona,

find that turquoise,

then it has to go to a lapidary, which is the person

that actually cuts the stones into a cabochon,

which is a stone that's polished on top

and usually flat on the bottom.

So it makes a dome shape.

And finally, you need a jeweler that's going to take

that gemstone and mount it into a piece of jewelry.

Now, the metal that is used to mount that piece

of jewelry can be quite an expensive

in and of itself, especially if it's something

like gold or platinum.

So together, you form

this rather expensive piece of jewelry.

@Linostrack asks, Where do rubies even come from?

It turns out that rubies

or the mineral corundum can be found all around the world.

If you are interested in finding rubies

in the United States, you could even go

to North Carolina to ruby mines.

However, the most precious rubies,

the most sought-after rubies are from Burma.

There is an area of Mogok Burma

that has a huge city made up of many, many thousands

of people where their entire job is

to find rubies in a mountain of marble.

@Tailsnkitty asks, What are quote 'Blood diamonds?'

Unfortunately, minerals

and gemstones often hold a lot of value per volume,

which means they're very small,

but they're very, very expensive,

and thus, they have been embroiled in conflicts

and used to trade for weapons,

and oftentimes, can be directly linked

to conflicts and death.

Ethical sourcing is very important.

Currently, there is a process called the Kimberly process,

which can trace the origins of diamond crystals

before they get cut and sold into jewelry.

So if a diamond comes into the United States without

the proper certification from the Kimberly Committee,

they get confiscated by TSA,

and they're actually brought here

to the Smithsonian's National Museum of Natural History

so that they don't get traded out illegally.

@gDegenXPlay asks, How do you find your gems?

As the curator of gems and minerals, myself

and my team, go out and scout

for new minerals that have appeared on the market.

Recently, we acquired a crystal

of the mineral called sapphirine,

not sapphire, and it was one of my favorite acquisitions

because it happens to be the largest crystal

of sapphirine in the world,

and it came from a mine in Madagascar.

So those are all the questions we have today.

Thanks for watching Gem and Mineral Support.

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