Soapstone sampling

Two important factors are suggested by this model. First, the concentration of a trace element in a particular mineral (like talc) formed in this manner depends upon many factors including the size and charge of the ion (which eflFect the partition coefficient), the composition of the aqueous solution, the minerals present in the intrusive (determines D ), and the time or extent of reaction. Since talcose rocks of similar composition can be formed by various different processes, the differences in any of the factors noted above would result in different trace element contents. Second, since the assumption that the partition coefficients for antigorite, talc, and tremolite are similar appears to be true, one would expect their trace element contents to be similar. This means that a series of soapstone samples collected from a particular geologic body might contain different amounts of these minerals but that they all would probably be very similar in trace element content despite differences in the bulk element composition of the samples. 

To show that REE and other trace elements could be used to characterize soapstone formations, it was necessary to show that variations between geologic bodies were greater than those for soapstone samples found within the formation. For these studies instrumental neutron activation analysis (INAA) was used because of its sensitivity and preci-... 

Figure 3, Chondrite-normalized rare earth element patterns of soapstone samples from quarries in the Mbe-marle-Nelson County regions of Virginia and in Crete. For the Albemarh-Nelson quarries f — the two lines give the range of 12 samples analyzed, and for the Crete samples (O — O) the two lines define the range of 19 samples. Two artifacts made of soapstone from the Albemarle-Nelson quarries are shown. One — M) is a pot from a habitation site in Cherokee County, NC and the other (A-- A) a pot from a habitation site near the quarry in Buckingham County, VA.

Often samples from outcrops are collected with little knowledge of the geologic settings. While a geographical description of a location is important, it can be misleading. For example a series of soapstone samples taken from Lancaster and Chester Counties in southeastern Pennsylvania... 

Over 650 soapstone samples from the Labrador region have now been analyzed. Of these, 400 samples are artifacts from a large number of different sites. The archaeological sites represent an extensive spatial distribution, but they also come from sites representing the different cultural traditions that span over 4000 years of human activity along the Labrador coast. The detailed discussion of these artifacts is not the subject... 

Previous work had indicated that the variations of REE contents within an outcrop were less than those between outcrops (4) this conclusion required further testing for the Labrador quarries. The large Fleur de Lys quarry offered an excellent opportunity for this study. Figure 3 shows the REE patterns typical of Fleur de Lys quarry. Over half of the samples are parallel to and fall between curves 1 and 2. Although this pattern is characteristic of the soapstone in this formation, the pattern shown by curve 3 is typical of the samples found at locality 2 and one worked area (B) at locality 1. The difference between these similar types of REE patterns is in the size of the europium anomaly. In early studies, this kind of difference between soapstone samples from... 

Figure 4. Chondrite-normalized REE patterns for representative soapstone samples from outcrops in the Okak area. Curves 1 (O) and 2 (%) are the types of patterns found at the Cojfin Island outcrop curve 3 (x) is an outcrop at Moores Island curve 4 (Aj is typical of the Nutak outcrop.

A basic study of the chemical composition and structure of two soapstone samples to improve scientific knowledge of this marvelous mineral is reported here. An investigation about the effects of a sulfuric acid aqueous solution on the physical integrity of the stone is also performed to provide some clues as to the main causes of corrosion (acid rain), and so to the possible approach to avoiding it. Since the acid attack begins at the surface, it is the surface chemical composition and structure that controls the acid corrosion. 

To perform the desired investigations, two soapstone samples were used, both from Ouro Preto city, Minas Gerais State, Brazil. From a macroscopic point of view, the only difference between the two samples is their color one is light gray (the stone itself, since the powder is white) whereas the other is red-brown. The two samples will be denoted hereafter as SS 1 and SS 2, respectively [4]. 

In soapstone samples, a minor resistance to acid attack is associated with a larger magnesium and/or iron content in the stone. 

Figure 5. Chondrite-normalized REE patterns for some soapstone outcrops along the eastern U,S. Piedmont. The source is indicated by the abbreviation of the state. The Md. sample is from Ednor quarry, Montgomery County, MD Va. is from the Albemarle-Nelson County, VA quarry Pa. (A) and (B) are representative of the two types of samples from outcrops in Lancaster and Chester Counties, PA N.C. is from an outcrop in Watuga County, NC R.L is from Oaklawn, RI and Mass, is from Westfield, Mass.

Figure 7. (bottom) Utilization of soapstone or steatite trade in Virginia, Soap-stone from extensive exposures in Albemarle-Nelson Counties ( ) were found in over half of the habitation sites (O) in Virginia, most of them west of the fall line. The Madison County quarry (A) was used less extensively but in the same area, A relatively small outcrop near Chula ( ) was used extensively, being found primarily in habitation sites (O) of the fall line. Other samples in this region came from northern Virginia ( ) and Pennsylvania (X),... 

Figure 11, Utilization of soapstone by Eskimos on the central Labrador coast during the Middle Dorset period (200-600AD), The letters in circles (O) are the four quarries from which samples have been analyzed. The letters refer to the letters used in Figure 12 where the characteristic REE patterns are shown. The quarries near O k and Davis Inlet were utilized locally and in the Nain region. In addition material from northern Newfoundland (L) is found in this region as well as many samples for which the quarries have not been identified,...

While it is possible to draw some conclusions with regard to the utilization of soapstone from the four quarries sampled, less than half of the artifacts analyzed originated from these four sources. The similarities... 

Figure 12. Chondrite-normalized REE patterns from quarries and artifacts in Labrador and Newfoundland. Sample N is from the Fleur-de-Lys quarry on the east coast of Newfoundland L from an outcrop near the Viking habitation site at Vanse aux Meadows in northern Newfoundland F from soapstone outcrops in the Freestone Harbor region and M from outcrops of Moore s and Okak Islands on the central Labrador coast. Both E and A are artifacts which represent a group of artifacts having similar REE patterns but for which no quarry of origin has been found.

Figure 13. Chondtite-normalized REE patterns for soapstone from the central Labrador coast. Dashed curves (%--%) outline the range of three samples from the Moore s Island, Okak outcrops (M) and two artifacts made of this soavstone. The Eskimo Island (O) artifact is from a Labrador Eskimo site (historic period) in Hamilton Inlet and the Koliktakik (A) artifact is from a soapstone pot from a late Dorset Eskimo site in the Nain region. A sample of the soapstone outcrop near Vanse aux Meadows (L) is shown (0) along with the Viking spindle whorl (A) made from this material.

The other sample of particular interest was a spindle whorl from what is considered to be a Viking settlement at L anse aux Meadows in Newfoundland (16), A small (20 mg) sample of this unique artifact was provided by Parks Canada. After duplicate analysis of 10-mg samples, the material could be returned to Canada for further testing since INAA is a nondestructive technique. As can be seen in Figure 13, the spindle whorl has a very similar REE distribution pattern to a sample of soapstone collected from an outcrop about a mile from the habitation site (17). 

While some caution must still be used in interpreting how closely samples must match, it is clear that analysis of the REE in soapstone can be used to obtain new information about the utilization of lithic resources. The reasons that this group of elements can identify the source of soapstone are geochemical. Soapstone is a relatively rare lithic resource formed by fairly complex metamorphic processes which leave a "fingerprint in terms of the trace element content. The distribution of material with this "fingerprint will help archaeologists to imderstand the process and pattern patterns of resource procurement. However, the examples discussed above show that it is also important to know age of the artifacts to interpret the geographical distribution patterns. 

Figure 3. Chondrite-normalized REE patterns showing the range of patterns found for soapstone from the Fleur de Lys quarry in Newfoundland. Curves 1 (o) and 2 (x) represent range of concentrations for most of the samples curve 3 (%) is the somewhat different pattern that was more typical of the Locality 2 soapstone. Range of REE patterns typical of the soapstone outcrops at Peabody Point is shown by curves 4 (n) and 5 (m).

The matching of outcrop samples with debitage and other artifactual material is an ideal problem for computer-assisted pattern recognition techniques (8). The use of ARTHUR for the analysis of the soapstone from Labrador will be discussed in a future publication, but the important parameters for comparing soapstone are given in Table II. For this table, the samples from a given quarry were taken as one or two groups. The... 

To sirrmlate the effects of acid rain on soapstone, a 0.1 mol dm sulfuric acid solution was prepared, and cubic samples (5 mm X 5 mm x 5 mm) were immersed in 150 cm of the acid solution for 40 days. 

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