Striped flint (sometimes called banded flint) is a version of
flint
Flint, occasionally flintstone, is a sedimentary cryptocrystalline form of the mineral quartz, categorized as the variety of chert that occurs in chalk or marly limestone. Flint was widely used historically to make stone tools and sta ...
, with a more or less regular system of concentric dark and pale stripes, noted to resemble rolling waters.
Use
A large striped flint deposit is located in
Lesser Poland
Lesser Poland, often known by its Polish name Małopolska ( la, Polonia Minor), is a historical region situated in southern and south-eastern Poland. Its capital and largest city is Kraków. Throughout centuries, Lesser Poland developed a ...
, near the cities of
Sandomierz
Sandomierz (pronounced: ; la, Sandomiria) is a historic town in south-eastern Poland with 23,863 inhabitants (as of 2017), situated on the Vistula River in the Sandomierz Basin. It has been part of Świętokrzyskie Voivodeship (Holy Cross Prov ...
,
Ostrowiec Świętokrzyski
Ostrowiec Świętokrzyski (), often referred to as Ostrowiec, is a city in southeastern Poland, in the historical region of Lesser Poland, with 66,258 residents (as of 2021). The town is one of historic centers of Polish industry and metallurgy, ...
and
Iłża
Iłża () is a small town in Masovian Voivodeship, Poland. In 2006 Iłża had approximately 5,165 inhabitants. The town belongs to the historical region of Lesser Poland, and from its foundation until 1795, it was part of Lesser Poland’s Sandom ...
. Because of its rarity and distinctive look, local striped flint is in use today in
jewellery
Jewellery ( UK) or jewelry (U.S.) consists of decorative items worn for personal adornment, such as brooches, rings, necklaces, earrings, pendants, bracelets, and cufflinks. Jewellery may be attached to the body or the clothes. From a wester ...
and has become a regional export product.
Striped flint was mined by
Neolithic
The Neolithic period, or New Stone Age, is an Old World archaeological period and the final division of the Stone Age. It saw the Neolithic Revolution, a wide-ranging set of developments that appear to have arisen independently in several p ...
people near
Krzemionki Opatowskie village around 4,000 BC, and it was used in manufacturing of axes.
Geology
Upper
Jurassic
The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...
(
Oxfordian) striped flint from Lesser Poland consists mainly of α-
quartz
Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...
. Morphology of grains indicates that the quartz is not a product of
opal
Opal is a hydrated amorphous form of silica (SiO2·''n''H2O); its water content may range from 3 to 21% by weight, but is usually between 6 and 10%. Due to its amorphous property, it is classified as a mineraloid, unlike crystalline form ...
and
chalcedony
Chalcedony ( , or ) is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, while moganite is monocli ...
conversion, but it precipitated directly from the seawater. The
crystallinity is higher in the centre of a
concretion
A concretion is a hard, compact mass of matter formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil. Concretions are often ovoid or spherical in shape, although irregular ...
. Sometimes chalcedony is present, being a product of recrystalization of opal. Other minerals can be found in small quantities:
clay minerals,
iron oxides and hydroxides,
calcite,
feldspar
Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) felds ...
,
mica,
glauconite
Glauconite is an iron potassium phyllosilicate ( mica group) mineral of characteristic green color which is very friable and has very low weathering resistance.
It crystallizes with a monoclinic geometry. Its name is derived from the Gre ...
,
zircon
Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of t ...
,
tourmaline
Tourmaline ( ) is a crystalline silicate mineral group in which boron is compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is a gemstone and can be found in a wide variety of colors.
The te ...
and
rutile
Rutile is an oxide mineral composed of titanium dioxide (TiO2), the most common natural form of TiO2. Rarer polymorphs of TiO2 are known, including anatase, akaogiite, and brookite.
Rutile has one of the highest refractive indices at visib ...
.
Different colouring of individual bands is linked to an increased and decreased number and size of pores that brought about different light reflection. Fewer and smaller pores reflect less light.
[Paweł Król, Zdzisław Migaszewski]
Rodzaje, występowanie i geneza krzemieni. Zarys Problematyki. Historia krzemienia
(Types, localization and genesis of flints. Outline. History of flint), Muzeum Narodowe w Kielcach, 2009, p. 45
References
Flint (rock)
Świętokrzyskie Voivodeship
Quartz gemstones