This microblade from the Hunter Valley, New South Wales, is made from heat-treated silcrete.  Microblades in Australia were part of a technological package that included backed microliths.  The technology proliferated in the Late Holocene, after about 5000 BP.

---

The flake in this model meets the criteria for a microblade; it is about 2.6 times longer than wide, measures less than 60 mm long, and was struck from a unidirectional core.  The red colour is typical for heat-treated silcrete in the Hunter Valley.  Heat-treatment is a technological process that involves cooking the stone in an earth oven.  When done correctly, the stone undergoes physical changes that make it easier to flake.  Heat-treatment also causes the stone to become more glossy and, if iron trace minerals are present, the stone takes on a red or pink hue.  The organisation of the flake scars on the dorsal surface of the flake show that it was struck parallel to the previous removals from the core, resulting in roughly-parallel edges.  It was probably struck by hard-hammer percussion and the platform was carefully prepared by flaking.

---

In archaeological terminology, a ‘blade’ is a flake struck down parallel ridges on a core face, and measures at least twice as long as it is wide.  The edges of the blade are approximately parallel.  The core face is maintained by prior removals, and blades are struck off in series.  If they are struck from one platform, the removals are ‘unidirectional’, and if they are struck from two opposed platforms, they are ‘bidirectional’.  Blades were struck by direct percussion (using a hard or soft hammer) or indirect percussion using a punch; or they were pressed off using a pressure technique.  This involved placing the end of the indentor onto the platform edge and applying a load—either by hand or using a lever—until the crack initiated.  The placement of the indentor and the amount of applied force can be precisely controlled, resulting in extraordinary control of the size and shape of the resulting pressure blades.  A common approach was to set up the core so that most of the blades had a trapezoidal cross section; these are called ‘prismatic’ blades.

Flintknappers in Australia made ‘macroblades’, measuring longer than ca. 60 mm long, and ‘microblades’, measuring less than 60 mm long.  The size cutoff between the two is an arbitrary  convention and the cutoff-point can differ between archaeologists.  All macroblade technologies in Australia involved the hard-hammer percussion technique.  Most microblades appear to have also been made by hard-hammer percussion, but the small platform sizes and bending initiations seen on some microblades may indicate the use soft-hammer percussion, using a soft stone or wood indentor.  The pressure or indirect percussion techniques were not used in Australia to make blades.

In many Australian technologies, the flakes vary morphologically outside the strict archaeological definition of blades.  These are considered ‘blade-like’ flakes, or are considered elements of a small-flake microlithic technology.  The pattern of striking parallel flakes from the core, and maintaining straight arrises on the core face, are aspects of blade production.  Blade technologies were common in Australia by the Late Holocene, after ca. 5000 BP, with some blade or blade-like technologies emerging by the Middle Holocene, ca. 10,000 BP.  Microblades and small blade-like flakes served as blanks for backed microliths.  Blade technologies were used across eastern, northern and central Australia, but are absent from Tasmania and are uncommon in southwestern Australia.