Marisa Giorgi, Information Officer, Queensland Museum

Grindstones are a relatively common tool found across Australia. But did you know grindstones have many varied uses? Archaeological science is revealing the complex nature of these stone artefacts.

Introduction

At Queensland Museum we have many grindstones of different shapes and sizes from across Queensland. These grindstones represent durable examples of everyday items used by Indigenous Australian people.  They are also integral components of the archaeological puzzle that helps us understand our past.

What’s a grindstone?

A grindstone is usually a large flat sandstone rock (abrasive rock) that is used with a suitable top stone, or muller. They form an efficient tool to grind or crush food to release nutrients. An important role was grinding of seeds to make flour for bread. This usually required a flatter top stone. There were many other uses which sometimes involved a smaller more rounded top stone called a pounder. This served to crack open seeds, break bones to extract the marrow, pound plant fibres to make string and grind ochre to create different pigment colours. Sometimes the process was dry grinding and other times using water. Essentially the main use of grindstones was for processing food.

Grindstones can be identified by their shape and wear patterns. Some are deeply abraded, with surfaces often worn smooth from extended use. They were mostly found where Aboriginal people lived and processed food. Grindstones were sometimes heavy (up to 14kg or more) so they were not always convenient to carry. The largest grindstones often remained at certain location for extended periods. Grindstones did wear out, and many areas lack suitable sandstone outcrops to create new ones. A grindstone trade network existed, and some of the recently located production areas are so large that they indicate an extensive and well-developed production for trade. Some areas, including parts of Victoria, seem to have fewer grindstones.

What can they tell us?

We can analyse surfaces of grindstones for traces of plant matter. Because of limited resources this research is only carried out with community permission. Grindstones with a lot of contextual information are generally selected for this research. For this reason it is always important to leave artefacts in situ (In place) when possible. Record the location and report your discovery to the Department of Environment and Heritage so that archaeologists can get the full story behind an object. You can play an important part in preserving Australia’s history.

They are not all the same….

In the Museum we have some very specialised grinding stones such as the Morah grinding stone- only found in the Wet Tropics rainforests. This grindstone is made of slate with several incised parallel grooves on its surface to create a processing platform for seeds and nuts. Starch residue analysis on some of these Morahs provide evidence that the stones were used to process toxic starchy nuts.

Some foods contain toxins which must be released before consumption.  Processing methods included water leeching or washing, and grinding or crushing. Grinding stones also processed plants for medicinal use. Smaller grinding stones were usually used in the production of pigments, crushing different colours of ochre to make a fine powder for the use in painting rock art, for painting on people’s bodies or on objects such as message sticks and shields.

Grindstone technology dates back thousands of years in Australia. Researching them provides us with clues about the food sources that were exploited across different climatic periods. Studies also shed light on the distribution of populations around Australia and how they traded and interacted. Some stones can even be traced to their origins before starting their life as a grindstone. One grindstone recently discovered in the Madjedbebe rock shelter, in Mirrarr Country, in northern Arnhem Land traces grindstone technology back over 60 000 years ago. That is the earliest evidence in the world for grindstones.

Grinding food, herbs and spices between two stones is still carried out today in many traditional communities. Indeed the mortar and pestle remains a popular tool in plenty of modern kitchens. Grindstones are still relevant to indigenous communities today, offering another connection to country and culture. At the Queensland Museum we have procedures in place to facilitate people visiting and reconnecting with their significant objects.

As we have many archaeological artefacts uploaded to our Collections Online web pages, you can start exploring some of the grindstones from the collection here.