This type of artifact is called an adze blade. The adze configuration has the blade hafted at right angles to the handle (different by 90 degrees from the orientation of the axe blade that is more familiar to Europeans and Americans). It was used for many different tasks, but the motion often ended with the blade coming back toward the user. Of note on this piece is the substantial corrosion over the entire surface. The vast majority of stone materials used for tool-making in the Neolithic period DO corrode, albeit slowly.
A small fraction of the pieces that have been found were made for ritual use, rather than true work. This is borne out by the fact that many of them have no chips or other marks of hard use. This is NOT the case with this piece. It clearly was used, and used hard. The chips on this tool are corroded to the same extent that the other parts of the surface are. This points to the chips having been made in antiquity, so that the depressed surface had about the same period of environmental exposure during burial as the rest. When this is NOT the case, it might point to a more complex history. However, the damage from use in work may have NOT been done by the creators of the piece. It could have been uncovered one time (or many times) in the course of the last 4000 years.
The people who uncovered it might have no compunction about making it into a working tool. In the last century, they have been viewed (by outsiders) as art, artifact, or a piece of history. Over the last few hundred years, the minority groups have viewed the finest ones as mystical objects to be used for shamanic purposes. The large simple ones were often still just tools. An example of this can be seen at the Museum of Ethnology in Hanoi. A chopping block in the reconstruction of a kitchen of a family of the Thai minority is in fact a Neolithic chopping block, reused but NOT repurposed. It is now what it was 4000 years ago a very durable tool.
This stone axe was found in Ha Tay province, very near to Hanoi. It is between 3500 and 4500 years old, the approximate dates of the Phung Nguyen Period (so named for the town near Hanoi at which the first artifacts of that culture were first found). There is some chance however, that it even older (by 500-1000 years). Tools of similar size, shape, and workmanship were also made by the Halong Culture, from farther north and east. However, their objects are much less common than are those of the Phung Nguyen period. For that reason, we think that our original attribution is the one most likely to be correct.
Prior to the advent of bronze - casting, stone was the major material used for tools, implements, and jewelry. During the Neolithic (New Stone Age) Period, techniques evolved to create the elegant shapes and highly polished surfaces that distinguish Neolithic tools (especially those of the late Neolithic) from objects of the earlier Paleolithic (Old Stone Age) Period. A variety of large tools were produced, to be either held directly in the hand or else mounted (hafted) on a wooden or bamboo handle.
A much smaller number of tools were made for finer tasks, such as carving wood, preparing medicinal herbs, etc. These small tools have a number of characteristics: they are usually of finer craftsmanship than the larger ones; they are more often of harder stone, and the stone used is often more intrinsically beautiful. The very high amount of time and effort required to create objects of this quality was feasible only for small tools and also made functional sense in the context of the more precise nature of the tasks for which they were made. Because of their small size, they are easily overlooked by farmers who uncover them in the course of farming, digging wells, etc. This accounts for their rarity, especially in relation to the larger tools, which are always evident when unearthed.
Tools of the New or Old Stone Ages era were, by definition, made without the use of metal tools. All working of the stone had to be done with other, harder stone - either the stone itself or dust from it (in effect, ancient sandpaper. True Neolithic pieces can be distinguished by the marks left behind by the techniques used in the manufacturing process. Often, they have a step - off on one or more surfaces. These irregularities are an outgrowth of the technology used in creating small flat surfaces. This involved using string impregnated with jade dust or other abrasive to wear a groove into a larger stone. Once the groove had reached a sufficient depth, the string was removed and a wedge placed into the groove just created. When struck with a mallet, the remaining stone was cracked off, which saved many hours of work. If the line of the break thus created was not exactly continuous with the created groove, the step - off was created. The amount of work needed to eliminate the discontinuity was prohibitively high, so it was rarely done.
The stone itself ages - in some cases very little, in other cases a great deal. Some of the larger tools were made of a tan stone a bit like sandstone. This allows extensive degeneration, leaving a powdered coating over the entire tool. Harder stone may age very little. However, in some soils, the stone absorbs iron compounds, acquiring a rust or terra - cotta color. Some of the stones that started out as a dark color (shades of brown, black red, or green) acquire a tan or white skin over the entire surface. This skin can sometimes be rubbed off and the original color revealed. However, most people prefer to leave it because it is a good indication of a surface that has been exposed to the environment, especially moist soil, for many centuries, or even for millennia.
Also, the blades often have one or more generations of chips in the surface. Some of these chips are a function of damage done in the course of the original work they were created to do. In this case, the chipped surface, having been exposed to the same soil for the same amount of time, has acquired the same color surface as the rest ob the tool. However, sometimes the chips are very recent, often caused by the shovel that uncovered them in the recent past. The newly broken surfaces are of a markedly different appearance than the rest of the tool (as a function of having not been exposed to the environment for centuries. This is a good indication that the piece was, in fact, created in antiquity.
This is true in the case of your piece. The tan skin covers the entire piece. Often, we see one chipped area that is of recent origin, probably made by the shovel or other tool of the man who found it, as he hit the stone blade while digging in his fields. The skin is good proof that the shaping of the tool and its loss under the soil was millennia ago. We know from the shape of the blade and the workmanship that this was probably made late in the Neolithic Period (New Stone Age), either during the Phuong Nguyen period (3000 to 2000 BC) or earlier. The Neolithic Period ended, in Vietnam, about 1500 BC (about 3,500 years ago), when people in this area gained the ability to extract copper from its ore and therefore were able to make and use bronze. This, by definition, signaled the simultaneous start of the Bronze Age and the end of the New Stone Age.
(Source: 54 Traditions Gallery, MSR 2012)