Stone Type: Igneous

Igneous Celt, North Carolina

‘Igneous’ is a catch-all term to describe rocks formed when molten magma cools and solidifies.  Intrusive igneous rocks form below the Earth’s surface, usually resulting in relatively coarse-grained stones like granite or diorite.  Extrusive igneous rocks form when magma reaches the surface and cools and solidifies rapidly.  These are also called ‘volcanic’ rocks.  Volcanic rocks are often finer-grained and suitable for flaking, such as basalt, rhyolite, or obsidian.

Volcanic

Extrusive igneous rocks form when magma reaches the surface and cools and solidifies rapidly.  These are also called ‘volcanic’ rocks.  Volcanic rocks—such as basalt, rhyolite, and obsidian—tend to be more glassy and suitable for flaking than intrusive igneous rocks like granite or diorite.

Soa core 11

Bifacial Core

Mace head 2

Club Head

Mace head 1, PNG

Club Head

Axe, Gold Coast

Facetted Axe

Hafted axe, Australia

Hafted Stone Axe

Mace head, Peru

Mace Head

Core 10, Soa basin

Multiplatform Core

Core 9 So'a Basin

Multiplatform Core

Core 7, Soa Basin

Multiplatform Core

Core 6, Soa Basin

Multiplatform Core

Multiplatform Mata Menge 7

Multiplatform Core

Core 8, pick, Soa Basin

Multiplatform Core, ‘Pick’

Core 4 soa basin

Retouched Cobble, ‘Perforator’

Adze, Langda

Stone Adze

Axe Willeroo Yard NT

Stone Axe

Basalt

Basalt is known as an extrusive igneous rock because it was erupted by volcanoes as molten lava onto the Earth’s surface.  It is usually black or dark gray in colour and weathers to dark green or brown.  It tends to be dense and fine-grained and is often suitable for stone-flaking.  Vesicular basalt is full of holes from air bubbles and is less useful for tools.  Basalt is rich in iron and is composed of ca. 45-52% silica.

Flake, basalt Anaiwan 1

Flake

Hafted adze Puke Ariki

Hafted Stone Adze, reconstructed

Samoan adze GSP

Modern Art, Galumalemana Steven Percival

Core, Tanzania

Oldowan Core

Adze, Java

Stone Adze

Samoan adze 7

Stone Adze

Samoan adze 6

Stone Adze

Samoan adze 5

Stone Adze

Samoan adze 4

Stone Adze

Samoan adze 3

Stone Adze

Hawai'i adze

Stone Adze

Samoan adze 2

Stone Adze Blank

Samoan adze 1

Stone Adze Blank

Axe Mithaka 1

Stone Axe

Axe, Ecuador

Stone Axe

Axe from Retreat

Stone Axe

Axe, Anaiwan 2

Stone Axe

Axe, Anaiwan 1

Stone Axe

Obsidian

Obsidian is a volcanic glass that forms when lava cools so rapidly that the atoms are unable to organise into crystals. Obsidian occurs from a specific form of lava and the composition is similar to rhyolite and granite.  The glass can recrystallise over time, leading to patches of white crystobalite crystals within the glassy matrix. 

Obsidian Aztec blade

Blade

Aztec pressure blade core re-do 1

Blade Core

Multiplatform core, Azerbaijan

Core

Macroblade core, Azerbaijan

Macroblade Core

Macroblade knife, Papua New Guinea

Macroblade Knife

Mataa Point 2

Mata’a Point

Mataa Point 1

Mata’a Point

Flenniken biface

Modern Art, J. Jeffrey Flenniken

Biface, Simon Greenwood

Modern Art, Simon Greenwood

screenshot (6)

Modern Art, Ted Orcutt

Rhyolite

‘Igneous’ is a catch-all term to describe rocks formed when molten magma cools and solidifies.  Intrusive igneous rocks form below the Earth’s surface, usually resulting in relatively coarse-grained stones like granite or diorite.  Extrusive igneous rocks form when magma reaches the surface and cools and solidifies rapidly.  These are also called ‘volcanic’ rocks.  Volcanic rocks are often finer-grained and suitable for flaking, such as basalt, rhyolite, or obsidian.

Clovis platter biface Maine

Bifacial Core

Flake, wedging initiation, Australia

Flake

Gorget broken NC

Gorget

Kolea stone

Kōlea Stone

Granite

Granite is an igneous rock that forms under the ground by the slow cooling of magma.  It is higher in silica content than diorite.  The coarse structure of granite makes it unsuitable for refined percussion flaking, but it was often shaped by pecking and grinding into durable tools like stone axes.  It was widely used for making sculptures and as building stone, and is familiar today as a popular material for headstones and countertops.

Discoidal, Illinois

Discoidal

Axe Fitzroy Station

Grooved Stone Axe

Diorite

Diorite is an igneous rock that forms under the ground by the slow cooling of magma.  It contains a lower proportion of silica than granite.  The coarse structure of diorite makes it unsuitable for refined percussion flaking, but it can be shaped by pecking and grinding into durable tools like stone axes.  It was widely used for building stone and making attractive sculptures.

Alunda Moose, Sweden

Ceremonial Battle Axe

Axe, vivien muller

Grooved Stone Axe

Axe Kimberley The Temple

Stone Axe