May 08, 2021

3 Quartz Properties to Know- so You can Crystal Shop with Confidence

I couldn't believe how blatant these mix ups were! Most of the time rocks shops get mineral names correct. But sometimes mistakes happen. Here's a few I've seen...

purple fluorite mislabeled as amethyst (in a rock shop)
graphic granite (quartz and feldspar intergrowth) being sold as "moonstone" (online rock shop)
"green quartz" that was adventurine (online IG seller page)

Since mineral labels DO get muddled- its not a bad idea to arm yourself with tools and knowledge. And empower yourself as crystal consumer.

So in this blog post, I'm giving you some introductory mineral identification tools for your tool belt. But just a few.

Don't want that tool belt dragging on the ground or so over-stuffed you can find anything.

Here's 3 diagnostic properties of natural quartz crystals. (Properties 2 & 3 are specific to crystalline quartz.)

Quartz Property #1- Hardness: 7

The Mohs Scale of mineral hardness informs relative resistance to scratching. Stick with me here... This scale's been around since 1822 and gives a numbered system of common minerals from softest to hardest.

Talc (chief ingredient in baby powder) is the softest mineral (its a 1) and diamond's the hardest (at 10). Quartz has a hardness of 7.

Here's how you can use this property to tell if your quartz is actually quartz...

The scratch test

Let's say you have two clear-ish, similar looking minerals and one's topaz and one's quartz. Topaz is an 8 on the Mohs hardness scale. So the topaz will scratch the softer quartz. But quartz cannot scratch topaz. See pic below for proof!

When I took mineralogy courses in college, I carried a hard plastic pencil box in my backpack with a streak plate, a nail, a tiny quartz point, a penny, and a glass plate (among other weird things). All these tools were for mineral hardness identification. A nail is a 6.5 on the Moh's scale.

Here's a great Mohs hardness scale image from the National Park Service- that also shows the hardness of common objects you can use to test mineral hardness.

Quartz will scratch all the things on this chart with lower hardness number (including the nail).

So if you've got a suspicion of a mix up between amethyst (purple quartz) and purple fluorite (hardness 4)- go for the hardness test! You know what to do! (But maybe pick a not so noticeable spot on the mineral.)

Quartz Property #2: Crystal Shape

Naturally formed quartz crystals grow in a characteristic shapes- that is if they take on shapes.

Anhedral vs. Euhedral

Quartz forms in structured natural crystalline shapes AND as masses/ chunks that don't have consistent shapes or distinct angular faces. When crystals are massive and not shaped, they're called as anhedral. Euhedral describes natural shaped minerals with recognizable crystal faces.

This example shows an anhedral rose quartz next to a euhedral smoky quartz crystal. (By the way, rose quartz, which is different from pink quartz is always anhedral. You can learn more about rose quartz and what makes it pink by reading this blog post.)

Un-natural (modified) quartz shapes

Rocks and minerals routinely get cut and polished into shapes (towers, hearts, spheres, etc.) and quartz is no exception. Obviously, only the natural, euhedral crystal shapes are a diagnostic property for quartz.

Hexagonal prisms

Natural quartz crystals form as hexagonal (six- sided) prisms. They're made of helical tetrahedral chains of SiO4 (with two of the O's being shared- hence the actual chemical formula of SiO2.).

Hexagonal quartz prisms have points at one or both ends.

This picture is taken looking directly at the point of a smoky quartz crystal. Count the sides. Go on.

(Please note- many other crystals also form hexagonal shapes, so this property alone isn't always diagnostic.)

Natural quartz is NOT...

If you see a crystal shaped as a cube, pyramid or rhombohedron- it's not quartz. Unless it was carved into that shape by a lapidary artist.

More on quartz crystal shapes (crystallography)

Unfortunately, the crystallography section of mineralogy class was a giant snooze fest (for me anyway). However, if you're into that (and if you are, you're a special one indeed)- check out this very comprehensive review of quartz crystallography (that's also easy-ish to understand). Here's the link: http://www.quartzpage.de/gen_struct.html

Quartz Property #3: Perpendicular Striations

Tiny horizontal grooves line the prism faces of quartz crystals. Sometimes they're so faint they're barely detectable- but sometimes they're so prominent you can feel big ridges with your eyes closed.

On quartz crystals, striations are perpendicular to the length of the prism and they're never seen on the point faces.

Many other minerals have striations so the presence of striations (or growth lines) alone isn't diagnostic. But most of the other minerals striations' are parallel to the long axis of the crystal. Not quartz.

Check out this pic of striations on smoky quartz.

Go forth and identify quartz

There's a whole laundry list of quartz properties, but these 3 important ones are enough to get you started confidently identifying natural quartz crystals.

Now go forth and observe your minerals. Just be careful not to scratch up all the minerals in your collection...

Now, I've got some questions for you...

Have you ever seen any mineral mix-ups? Do you have any mineral identification tools in your tool belt that helped you in a shopping experience? What's the weirdest thing you found in your purse?

Send me an email and let me know! shalina@truthminerals.com