Silicate raw materials

Quartz (Sio2) is the most constant of all minerals, and fine grained variants of this mineral (silicates) were often utilized to make tools.

In this group are included those minerals whose composition does not depart significantly from SiO2. Some varieties are crystalline and include quartz, tridymite and cristobalite; others, generally grouped as chalcedony, are cryptocrystalline. Opal is amorphous.
(Hamilton et al 1976, 128)

Flint

Flint can be found in the creaticous layers that were deposited more than 50 million years ago at the bottom of the ocean that once covered parts of North Western Europe (Petersen 1993:21). Flint consists of microscopic quartz crystals and exists in many variants. Flint can be found as nodules, tabular plates, sausage-shaped etc.

ADD SECTION: NB: Chert is a misunderstood term that is often applied to a coarse variant of flint. Geologically flint and chert are the same. The name chert is used to describe bedded, massive chalcedony, and the name flint is reserved for the black, nodular variety commonly found in chalk.(Hamilton et al 1976,, 130)

• Appearance: Flint has many different appearances dependent on how it originated.
• Fracture: Conchoidal fracture
• Grain size: Fine-grained
• Properties: Homogenous, brittle, elastic, sharp edges
• Tools: All kinds of tools
• Source: In Norway, limited to icetransported nodules along the coast ADD INTERNATIONAL
• Relevant literature: Many overviews of flint exist; see Petersen 1993; Thomsen 2000; Knarström 2001.
• Colour: Blue-grey, grey, to nearly black when fresh, but weather to a whitish, powdery crust (patina).
• Texture: Very fine-grained and smooth; conchoidal fracture. Rough on weathered surfaces.
• Structure: Flint and chert form rounded nodules of widely differing forms, but chert also forms massive beds. Flint nodules are often hollow and may contain a fossil, such as a sponge or echinoid.
• Mineralogy : Composed of silica, mainly the variety chalcedony. Some authors distinguish flint and chert compositionally but the differences, if any, are slight.
• Field relations: Flint and chert nodules occur typically in limestone and chalk. They are usually patchily distributed but often concentrated along one bedding plane. Their origins are not fully understood; but some appear to be secondary replacements of the host rock, whilst others may represent primary deposition on the sea bed of colloidal silica.
• (Hamilton et al 1976, 204)

 

Chalcedony

"Chalcedony is the name given to compact varieties of silica which comprise minute quartz crystals with sub-microscopic pores. There are two main varieties: chalcedony, which is uniformly coloured, and agate which is characterised by curved bands or zones of differing colour."
(Hamilton et al 1976, 130).

It has conchoidal fracture and therefore has the same knapping qualities as flint.

flint, chert, carnelian, and jasper are all varieties of chalcedony.
Chalcedony is the name applied to a number of variants of silicates that each consist of cryptocrystalline quartz.

• Appearance: There are two main variants of chalcedony. One is called chalcedony and has one single color. This color can vary based on the mineral content. Iron minerals for example give a red/yellow color. The other variant of chalcedony is agate, in which quartz grains are arranged in layers and their build up is clearly visible in the different colored layers. (Garmo 1983:66; Hamilton et al 1976:130).
• Fracture: Conchoidal fracture
• Grain size: Fine grained (cryptocrystalline)
• Properties: Homogenous, brittle, elastic, sharp edges, color
• Tools: All kinds of tools as long as the blanks are big enough, small tools and blades are most common.

Jasper

Jasper is opaque chalcedony and is generally red, but yellow, brown, green and grey-blue varieties occur. Jasper is rarely uniformly coloured, the colour is often distributed in spots or bands.
Hamilton et al 1976, 130)

Jasper is non-transparent chalcedony

• Appearance: Jasper is often red, but can also be found in variants of yellow, gren, brown and grey-blue. Jasper is rarely one-colored (Hamilton et al 1976:130).
• Fracture: Conchoidal fracture
• Grain size: Fine grained (cryptocrystalline structure)
• Properties: Homogenous, elastic, brittle, sharp edges, color
• Tools: All kinds of tools as long as the blanks are big enough
• Source: Flendalen i Trysil, Hedmark and Trondheimsfeltet
• Relevant literature: See Sjursjeike 1994

Quartz

Quartz consists of Sio2 and is the most common mineral on earth. Quartz is a hard mineral and occurs in many different variants, both as crystals (see rock crystal) and as more or less crystalline. The quality of quartz is dependent on the crystal structure and whether or not these compounds are weak or strong. If they are weak the quartz will fragment easily and somewhat uncontrollable. If they are strong, the quartz can be more easy to flake in a controlled manner. However, the crystalline structure will always cause quartz to fragment more frequently and to a higher degree then other raw materials.

Quartz is composed mainly by SiO2, and its structure is crystalline.

Quartz occurs in many varieties. Rock crystal is colourless quartz and sub-varieties include ghost quartz in which growth stages are marked by inclusions, and rutilated quartz (sagenite), which contains hair-like rods of rutile. Amethyst is purple; milk quartz is white; rose quartz is rose-red or pink, and is usually found massive rather than as crystals. Citrine is yellow and transparent and resembles topaz. Smoky quartz (sometimes called cairngorm) is smoky brown to nearly black. Some quartzes contain impurities that not only impart a colour but render them opaque. Ferruginous quartz is an example of this and is commonly brick-red or yellow.

Distinguishing features: Crystal form, conchoidal fracture, vitreous lustre, hardness.

Occurrence: Quartz is one of the most widely distributed minerals.

(Hamilton et al 1976, 128)

• Appearance: The different variants of quartz results from a difference in crystal structure and/or mineral pollution causing the quartz to change color. Rose quartz, for example, contains iron. Below some variants of quartz are shown: transparent quartz, smoky quartz, rose quartz and milky quartz.
• Fracture: Often undefined irregular fracture along crystal planes (some variants of quartz, however, may have a conchoidal fracture caused by strong crystal compounds i.e milky quartz).
• Grain size: No grain size due to a crystalline structure.
• Properties: Brittle, sharp edges, available, color
• Tools: Suitable for projectiles and smaller tools like knives and scrapers.
• Source: Appears everywhere, and is the most common mineral.
• Relevant literature: A lot of research on quartz has been carried out in Sweden and Finland (see for instance Knutsson 1988; Lindgren 2004; Callahan et al 1991; Rankama 2003; Callhan 1987; Carlsson 2001; Carlsson et al 2004; For Norway see Eigeland 2007)

Rock Crystal

Rock crystal is quartz in pure crystal form, both single crystals and groups of clear quartz (Garmo 1983).

Rock crystal is quartz in crystalline form and is translucent.
It has conchoidal fracture and therefore ideal for making tools.

• Appearance: Clear, transparent crystals
• Fracture: Due to large crystals the rock crystal has a conchoidal fracture.
• Grain size: No grain size due to a crystalline structure
• Properties: Homogenous, brittle, sharp edges, available, the pure crystals
• Tools: The natural crystal planes of the rock crystal are perfect for microblade production. Tools like scrapers, knives and projectiles can also be produced from rock crystal.
• Source: Rock crystal is available across the country in bigger and smaller amounts.