What is the difference between Flint and Chert?

Here's a good question.

There doesn't seem to be a single answer. I've heard several explanations.

One I read was about quality, there is only chert, flint is simply a colloquial word used for good quality chert. So the grey stuff full of yucky inclusions and barely knappable is chert and the nice pure black stuff flint.
http://www.assemblage.group.shef.ac.uk/4/4hind.html

Last year I attended a geology course and the teacher, a doctor of geology was insistant that flint forms in chalk and chert in limestone, quality is irrelevant. Good or bad, black or powdery grey, fine or course grained, it's flint if it come from chalk, and chert from limestone.

Another explanation I just read was grain size. If it fine grained it's flint and course grained it's chert, regardless of quality or where it formed.
http://www.theaaca.com/Learning_Center/flintvs.htm


So with three conflicting and seemingly knowledgable explanations, I'm still none the wiser.

Frankly, I wouldn't recognise a piece of chert if it jumped up and waved at me.

Although Scotland is flint poor, I have been told to look out for chert. I live near old limestone workings, so have wondered if it is worth looking.

As I said though, no clue what I'm looking for. Also, it needs to be dug as it doesn't weather well?

Yeah, the geology of Ireland, Wales, Scotland and NW of England is not great for knappers. Normally South England's pretty crap compared to Scotland for outdoor thing, you get all the scenary, mountains, ignious rocks ects, but knapping is one advantage of living on a former sea bed, you get great flint. I did a quick google picture search for 'arrowheads scotland' and found a few, one advantage of chert is it comes in many colours.

There's almost no flint in the US, so it's mostly done with other stuff, chert being the most common, do a You Tube search for 'chert' to see people out walking finding the stuff and chert knapping to see it being worked.

Unlike flint chert has no cortex and it also need heat treating before you knap it.

I would go with the geologist's definition, invariably they are more objective than lithic "experts" can be.

Contrary to the above explanation I would propose that cortex is simply the weathered rind. It is not possible to distinguish chert and flint from one another by whether or not they have a cortex but rather their origin.

Hi,

Flint is the name specifically given to the form of quartz that occurs in nodular and tabular form in the chalk. In Britain, you also sometimes get large masses of similar minerals in other limestones that are usually referred to as chert. I think some confusion arises because in the US they usually refer to all forms of flint as chert and (as I understand it) rarely use the word flint except maybe in connections such as gunflint.

I understood there was no flint in America, just chert. That is if you go on the Limestone/Chalk formation distinction, but they tend to refer to it as flint.

I think we're saying pretty much the same thing - it's not so much that there is no flint, as the fact that they rarely use the word in the U.S..

Mineralogically, there's little difference. The material in question is a form of microcrystalline quartz with any one of a number of possible mineral inclusions.

Different mineral inclusions give rise to
different colorations. The following are all forms of flint:
Agate, Carnelian, Chalcedony, Jasper, Obsidian, Onyx and Opal.

They all have similar origins: material from siliceous microscopic sea creatures is dissolved in seawater, then precipitates out in a jelly like mass and fills crevices in sediments that become limestones.

Thanks for clarifying that Richard, I think I get you now.

I've used quite a few of those you mention and some more, such as dacite and novaculite. Basalt is also a major knapping rock I would guess this being so chemically different from what you describe couldn't be called flint

An interesting excerpt from Understanding Stone Tools and Archaeological Sites by Brian P Kooyman which I'm currently reading.

"2. Chert/Flint: there is some disagreement about whether these two mineral categories should be included together or if they should be separated (e.g., Crabtree 1967, Luedtke 1992:56). For the most part, flint is not a term North American geologists use. Luedtke (1992:56) suggests that all materials such as flint, agate, chalcedony, and jasper be seen as varieties of chert. She notes that most often flint is used to mean dark chert found as nodules in chalk deposits specifically, but that this segregation does not work well geologically outside of Britain. In her definition, chert is a general term for all sedimentary rocks composed of microcrystalline quartz. I advise using Luedtke's all-inclusive definition of chert to include chalcedony, jasper, flint, etc., but for many archaeological discussions these need to be separated from each other. When flint is distinguished from chert, it is segregated based on a darker color (black, dark brown, gray), the dark color being due to organic matter included in the chert (Blatt et al. 1980:571; Monroe and Wicander 1995:131). In this segregation, chert is generally defined as lighter in color and as showing a broader range of colors. There are exceptions to this rule. Chert accumulations are generally either as beds or as nodules in carbonate rocks (Blatt et al. 1980:575). Flint is often defined specifically as the nodular form, particularly when the nodules occur in chalks or marls. Conversely, chert is a term often reserved for massive deposits in beds or layers. This categorization seems to be the most common definition used to separate these materials, as used by Whittaker (1994:70) for example, when separation is deemed necessary. Chert may also form as nodules in other material (e.g., limestone). To confuse the issue of this distinction further, chert nodules in limestones may be so abundant that they coalesce in the plane of bedding, forming discrete layers (Blatt et al. 1980:575). Chert is about 99% silica and less than 1% extracrystalline water (Blatt et al. 1980:571); generally it has less water than chalcedony (see below); it has a luster that is usually dull to waxy; it is opaque, although it may transmit light on thin edges; it may be banded and may have inclusions (fossils or other); it has a [Mohs'] hardness of approximately 7.0. Chert forms in a number of ways. Many of these formation processes also apply to chalcedony:"