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What Is Flint?

A microcope is needed to see the individual crystals in flint.
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  • Written By: Mary McMahon
  • Edited By: Bronwyn Harris
  • Last Modified Date: 24 April 2014
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Flint is a very hard and durable variety of quartz. It has been used by humans for thousands of years to make tools and build walls, among many other things. Several major sources can be found in the Northern Hemisphere, and the rock has a number of modern industrial uses. In addition to being included inside many things, flint can also be purchased in raw form, often from hobbyist shops and at rock shows.

Officially, flint is classified as a chalcedony. A chalcedony is a cryptocrystalline form of silica, and a number of minerals including agate and carnelian are also classified as chalcedonies. The term "cryptocrystalline" refers to the form which the crystals of silicate in the rock take. Although the rock is technically crystalline, the individual crystals are so small that they can only be distinguished with the aid of a microscope, unlike larger crystalline quartzes such as amethyst.

Like many rocks, flint is a sedimentary rock, formed over a series of centuries from an assortment of compressed sediments. It can range in color from almost white to black, although it tends to be primarily gray. The extreme hardness of this rock has made it a popular instrument for an assortment of tasks, since it does not readily break down. Early humans used it to make tools such as axes and arrowheads.

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Flint also has another unique property that many people are aware of. When struck against steel, fit lint will generate a spark by breaking off a small piece of the steel and heating it, causing the steel to ignite, feeding on the oxygen in the air. Although making a fire with flint and steel can be challenging, it is possible, and the rock is also included in devices like lighters, where it combines with steel above a robust fuel source to make a flame.

There are only a few hazards to humans posed by flint because it is not composed of toxic substances. The edges of broken pieces can be razor sharp, so caution should be used when handling this rock. In areas where flint occurs naturally, a fall onto broken pieces can be rather painful, and the rock has been known to slash through bicycle tires and lightweight pants, as well. Flint is especially common around deposits of chalk, so people should be cautious about going barefoot or participating in rough play in regions of the world with known chalk deposits.

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Discuss this Article

anon324615
Post 8

Flint as a weapon could be viable as a shard set in a wooden club, like obsidian and others.

anon317491
Post 7

Yes, you can use quartz instead of flint. It takes longer with quartz though, because it is not as sharp. But with flint, if you light it in three strikes, with quartz you will light with six or eight strikes.

aishia
Post 5

Now I'm curious...if flint is harder than quartz, hard enough to slash through bike tires and cut people's feet and not get dented when you hit it against steel, do you think it would make a good material to make knives out of? I mean, it cuts well, and it looks really nice. Are there such thing as flint knives out there?

Maybe making the steel ones takes less effort?

gimbell
Post 4

@SkittisH - Yes, your quartz crystals would work in place of flint if you tried making a fire using them and a piece of steel. As Malka noted here, the sparks created when you strike flint and steel together are really little melted bits of the steel flying off -- the fact that the flint is flint doesn't really matter.

In fact, you can start a fire using steel and any kind of mineral that ranks seven to eight on the Mohs hardness scale. If you have pendants that are made of Bloodstone, Agate, Jade or Jasper, they will work just as well too!

Of course, you might want to stick to flint just because "I can make a camp fire without matches using Agate and steel" just doesn't sound as impressive, at least not to me. Flint's kind of tradition at this point -- people expect it.

On the other hand... "I can make camp fires without matches with my Bloodstone and steel" sounds pretty cool. Hmm.

Malka
Post 3

@seHiro - You really do sound like you're speaking from experience! Ouch. Practicing is indeed a great piece of advice, and very important to learning how to do this skill.

I had a few additional words of advice here for anybody reading who wants to try using flint and steel to light fires:

It's ideal to have a piece of flint and a piece of steel that had angled edges that can clash -- pretend you're whittling off a piece of the steel by "slicing" it against the flint.

Slide the pieces across each other when you strike them -- don't clack them together straight at each other. You'll get more sparks with the "whittling" method.

The sparks created when you strike flint and steel are actually tiny molten blobs of steel that come off of the steel as a result of the heat from the friction between the flint and steel pieces. What this means is that the harder the type of steel is, the harder it will be for you to get it to make sparks, so pick a softer type if possible.

Lighting a fire with flint and steel is considered a manly and "tough" thing to be able to do, but it's great for people of any gender to know if they're lost in the woods, ran out of matches, and happen to have a flint and steel survival kit.

seHiro
Post 2

If you ever take a survival class and you bring along flint and steel thinking you'll be all big and bad and make fire without the use of matches, take this bit of advice from somebody who learned the hard way: practice first!

More specifically, practice before you're out in the damp cold forest clunking rocks together with fingertips that are going numb and wondering why there's sparks but your tender won't ignite.

Like anything, starting a fire with flint and steel is a skill -- the movies make it look easy, but they do that with everything! In real life, you've got to practice a lot to learn to make good sparks with your flint and steel, and even more to know how close to be to the tender to get the sparks to hit it, when to stop sparking and blow on the tender instead to fan the flames, and how hard to blow to avoid blowing the sparks out.

I recommend successfully lighting tender with your flint and steel at least three to five times before you try using the skill out in a practical situation. Practice makes perfect.

SkittisH
Post 1

I had no idea that flint and quartz were the same substance! I wonder if you could create a spark or start a fire striking quartz against steel? If so, that would make my quartz crystal pendants suddenly double as survival gear, would I think would be pretty sweet.

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