Two terms from the title require some elaboration. "Forensic" refers to evidence suitable for presentation in a court of law and, in this case, the jury consists of scientific peers who ultimately determine whether the evidence we have collected is suitable to support our conclusion that we have located the source quarry for the Titanic headstones. "Black granite" is the dimension-stone-industry term for gabbro.

Over the course of this investigation, 10 principles emerged for narrowing this search, and they should be useful for any similar type of search in future. These principles are as follows:

Using the principles above, we now present the quantitative, qualitative, and circumstantial evidence that the Charles Hanson quarry in Bocabec, New Brunswick (Fig. 3) is the source of the Titanic headstones in Halifax, Nova Scotia, approximately 500 km distant. We present this supporting evidence in order from the strongest quantitative to moderate qualitative to weakest consequential. In a departure from the format of a conventional scientific paper, we evaluate the strength of the evidence immediately following its presentation.

According to Principle 2, a matching age for headstone and quarry is a necessary, but on its own insufficient, condition to establishing a connection between them. A matching age for the Titanic headstones and candidate quarry is, therefore, the one quantitative value that must fit independent of any variation in mineralogy, texture, or bulk chemical composition.

Figure 4 and Table 1 show the results of the zircon age determinations by LA-ICP-MS. A combination of minor inheritance of older material, apparent recent Pb loss (pulling points to younger ages), and incorporation of common Pb has affected the grains. In most cases there was enough common Pb to apply a ²⁰⁴Pb-based correction to the data. In other cases we used a ²⁰⁸Pb-based correction if the measured ²⁰⁴Pb was too low. A few data points required no common Pb correction (e.g., Rit2-z1 – 5 in Table 1). Spots that record recent Pb loss and those with inheritance (presumably xenocrystic cores) were additionally filtered out until a single cluster of three or more near-concordant data produced a weighted-mean concordia age. These clusters typically comprise a combination of ²⁰⁴Pb-corrected, ²⁰⁸Pb corrected, and uncorrected data. Using this approach, the Baxter headstone has a concordant age of 421.0 ± 4.1 Ma, and a weighted-mean ²⁰⁶Pb/²³⁸U age of 422.1 ± 3.5 Ma (n = 5). The Ritcey headstone has a concordant age of 422.7 ± 2.0 Ma, and a weighted-mean ²⁰⁶Pb/²³⁸U age of 420.8 ± 3.4 Ma (n = 5). The Hanson quarry sample W467 has a concordant age of 422.3 ± 1.9 Ma, and a weighted-mean ²⁰⁶Pb/²³⁸U age of 421.9 ± 3.0 Ma (n = 7). All errors are 2σ. In combination, these three samples (Baxter, Ritcey, Hanson) yield a concordant age of 422.1 ± 1.3 (n = 17). The low MSWD (0.00058) for this data set indicates that there is no excess scatter beyond random analytical errors.

According to Murray (2004), “Finding similar properties in two samples does not in itself prove a common source. The significance of such evidence is determined by probability and statistics.” In the case of the LA-ICP-MS zircon ages, the chi-squared test for homogeneity (Kalbfleisch 1985) gives a significance probability P = 0.83, showing no evidence against the null hypothesis that the mean zircon ages of Baxter, Ritcey, and Hanson quarry are not different.

Olivine occurs as corroded, anhedral, individual or clusters of cumulus grains, poikilitically included in intercumulus augite (Fig. 5a). At the time of our analytical work on olivine, we had samples of the Baxter and Ritcey headstones, but only five samples from the Hanson quarry. The Baxter headstone and three of the five Hanson quarry samples contain olivine, but the Ritcey headstone and the other two Hanson quarry samples do not. The olivine analyses come from two polished thin sections cut from the Baxter headstone (T-orig and T-87) and two polished thin sections cut from one Hanson quarry sample (104A1 and 104A2) (Table 2). Altogether, we analyzed 11 olivine grains from the Baxter headstone and six olivine grains from the Hanson quarry. Table 2 also shows the number of analytical points for each grain, the mean FeO/(FeO + MgO) values for each grain, and the range of FeO/(FeO + MgO) values. The range of FeO/(FeO + MgO) values from a homogeneous olivine control sample (174.1) is 0.003 (n = 15), attributed to analytical error, indicating that most of the Baxter and Hanson olivine grains are chemically zoned. Because the olivine grains are anhedral relics, their precise locations in the former originally zoned crystals are unknown.

Figure 5b shows the 81 individual determinations of FeO/(FeO + MgO) in olivine grains (open circles) and the grain means (filled circles). We used a mixed-effects analysis of variance (Pinheiro and Bates 2013) to compare mean FeO/(FeO + MgO) values of olivine grains in the four polished thin sections, with a random effect accounting for the correlation between observations from each grain. A mixedeffects analysis compares the differences in sample means to the between-grain variation, rather than to the withingrain variation. We found no significant difference among the mean FeO/(FeO + MgO) values of the olivine grains in the four thin sections using a likelihood ratio test (P = 0.13). There is a large variance component for the grains, which quantifies the large differences among the mean values of the grains apparent in Figure 5b. Three of the five grains in 104A2 have high FeO/(FeO + MgO) values relative to the other grains, and these analyses are possibly from former rims rather than cores. The relatively large differences between the olivine compositions in two thin sections (104A1 and 104A2) cut from one sample (104A) underscore Murray’s cautionary comment quoted in Principle 9 above.

In conclusion, given that olivine FeO/(FeO + MgO) values can theoretically range from 0.00 to 1.00, it is remarkable that the values from the Titanic headstones and Hanson quarry occupy such a restricted part of this compositional spectrum, and that there is no significant difference between the mean olivine compositions in headstones and quarry.

The ideal condition under which to compare mineral compositions is that in which the mineral under investigation shows no chemical zonation. Petrographic examination with crossed-polarized light clearly shows that augite grains of the Titanic headstones and Hanson quarry are optically, and therefore chemically, strongly zoned. Because, in a twodimensional thin section, the three-dimensional cores of grains cannot be determined with any degree of certainty, we can compare only the rims (Principle 4). Figure 6a shows one of the analyzed augite grains from the Baxter headstone, and some of the laser-ablation craters around its rim (arrows), and Table 3 shows the average compositions of the augite rims.

The Appendix contains details of the analytical procedures and data processing. Most importantly, we also analyzed augite grains from two completely unrelated gabbros to test that there is no universal standard composition for augite rims in gabbros, in which case the statistical similarities between Titanic headstones and Hanson quarry would mean nothing in terms of establishing a connection between them. One of these unrelated gabbros is a pristine haplogabbro (HDG) of unknown age or origin, other than it was sold as tiles by Home Depot™ in about 2011, and the other is from 380 Ma Atwoods Brook gabbro pluton (ABG) in Nova Scotia (Tate and Clarke 1995), which is petrologically similar to the Titanic headstones.

Figure 6b shows conventional spider diagrams for seven major and 28 trace elements in the Titanic (THH), Hanson (HQB), HDG, and ABG gabbros to provide a general visual assessment of similarities and differences between the four sample means. The largest differences between Titanic and Hanson are in Li (8) and Cr (11). In addition, the REEs (21-34) have slightly greater concentrations in the Hanson augites, but the slope (fractionation) of the REE pattern and Eu (26) anomalies are similar. In contrast, HDG and ABG augite compositions normalized to Titanic show large differences for many elements, including the concentrations and fractionation patterns of the REEs, as well as the Eu anomaly (HDG is negative and ABG is positive relative to Titanic).

The box plots (Fig. 6c, d) provide a better qualitative visual comparison of the Titanic and Hanson augite rims, because they include the variance for each population. As with the spider diagrams, the box plots show small differences between Titanic and Hanson, and larger differences between HDG and ABG relative to Titanic.

To more rigorously assess all differences between Titanic and Hanson augite rims, we computed a likelihood ratio test for each element individually, by comparing the fits of two mixed-model effects models (Pinheiro and Bates 2013), with a random effect for grains accounting for the correlation between measurements within a single grain (Table 4). The smallest P-values were 0.0027 for Mn and 0.0027 for Li. Using a corrected threshold of 0.05/35 = 0.0014 for multiple comparisons (Bonferroni 1935), we found no statistically significant differences between Titanic and Hanson augite rims. These findings are remarkable, given that there must be millions of augite grains in the Titanic headstones, and billions of augite grains in the Hanson quarry, and yet the chemical compositions for 35 chemical elements from a “random” selection of three grains from the former and two grains from the latter show that they are not statistically different.

However, perhaps the compositions reported here are just some universal standard for augite rims in gabbros, in which case the statistical similarities mean nothing in terms of establishing a connection between the Titanic headstones and Hanson quarry. To at least partly mitigate this problem, we also analyzed 10 spots in the rim of one augite grain from the petrologically similar, but 380 Ma, Atwoods Brook gabbro (ABG) from Nova Scotia (Tate and Clarke 1995), and also analyzed 16 spots in the rims of three augite grains from the pristine haplogabbro of unknown age or origin (HDG). Figure 6d also shows the box plots for the augite rim compositions of these unrelated gabbros, and they appear to be different from the compositions of the Titanic and Hanson augite rims. Element-by-element comparison of these two gabbros to the Titanic samples shows statistically significant differences, with 11 ABG elements and 13 HDG elements falling below the Bonferronicorrected threshold of 0.05/35 = 0.0014. Clearly these two unrelated gabbro samples have their own distinctive augite-rim fingerprints, and this suggests that the good matches between the Titanic and Hanson augite rims are meaningful.

Table 5 shows the concentrations of 10 major elements elements, and 38 trace elements for five rocks from the Baxter and Ritcey headstones, and 12 rocks from the Hanson quarry (two from the walls of the quarry, W464, W467, and the remaining 10 from the abundant fresh angular blocks that were excavated but never removed from the quarry). Of the 12 samples from the quarry, we used the log-ratio distance for unweighted major-element compositional data (Aitchison 1986) to select the three samples (W470d, W471a, W471b) that are closest to the mean whole-rock chemical composition of the Titanic headstones. The log ratio distance is the Euclidean distance between the vectors of elements, transformed by taking the log of their ratio to SiO₂ to eliminate the effect of closure (constant sum).

Figure 7 shows conventional spider diagrams for 48 with the average of the three selected quarry samples normalized to the average of five Titanic samples (with such small populations, box plots are meaningless). For most elements, the mean whole-rock chemical composition of the Hanson quarry shows small differences relative to the mean Titanic headstone composition, with the exceptions of Cr (14), corresponding to the anomaly that also exists in the augite (Fig. 6b), Cs (24), U (30), and C (49). On the other hand, the bulk chemical compositions of the HDG and ABG gabbros appear to have few compositional similarities relative to the Titanic headstones. Clearly, this semi-quantitative, but highly visual, comparison of so many elements together shows that each gabbro has a unique chemical fingerprint.

To more rigorously compare whole-rock chemical compositions of the Titanic headstones and Hanson quarry, we excluded C, and the 10 major elements affected by closure, and used the ANOSIM approach (Anderson 2001) to jointly compare the remaining 37 trace elements. These trace elements are not subject to closure, so we used Euclidean distance instead of the log-ratio distance for this comparison. We also compared the elements individually using t-tests, and Table 6 shows the P-values for all pairs (THH-HQB, THH-HDG, and THH-ABG) and all elements, arranged by geochemical group. For all elements combined, there is no significant difference between the Titanic headstone and Hanson quarry samples [the lowest P-value for any component (Cr₂O₃) is 0.0141, whereas the Bonferronicorrected threshold for a significant difference for 37 elements combined is 0.05/37 = 0.0014]. Table 6 also shows the P-values and Bonferroni-corrected thresholds for LILE, HFSE, REE, TRANS, and OTHER groups of elements. If we apply the Bonferroni (1935) correction for multiple testing, we conclude that even the LILEs in the Titanic headstones and Hanson quarry are not statistically significantly different. If we include the two unrelated gabbros (HDG, ABG) in the statistical analysis, the test using all 37 trace elements shows many statistically significant (P = 0.0000) differences between Titanic headstones and the two unrelated gabbros.

The 422 Ma gabbros of Maine and bordering New Brunswick are highly differentiated, may even be layered, and are probably co-magmatic with the Bocabec pluton of the Saint George Batholith (McLeod 1990, McLaughlin et al. 2003). If layering is present in the Hanson quarry, it is not evident, perhaps because of the weathering of the walls. It would be easy to show that the ferromagnesianmineral-rich bottoms and felsic-mineral-rich tops of individual rhythmic layers in, for example, the Skaergaard intrusion are statistically unrelated, but such a statistical conclusion would be geological nonsense. So, in the case of the Titanic headstones and Hanson quarry, it is remarkable that the statistical similarity is so good. We expand on this matter of compositional matching in the Discussion.

In this section, we have presented, visually compared, and statistically tested four largely independent types of quantitative data [zircon ages, olivine FeO/(FeO + MgO) values, augite chemical compositions, and whole-rock chemical compositions]. In each case, we have shown that the Titanic headstones and the Hanson quarry populations are not statistically different. Even given that some of these parameters are not entirely independent [e.g., FeO/(FeO + MgO) in olivine grains vs. MgO and FeO concentrations in the whole rocks, or REEs in augite rims and REEs in whole rocks], a strong degree of overlap exists between the two populations for most other parameters (Figs. 4–7). Significant differences do exist for some individual components (e.g., Cr in augite rims and whole rocks), but these carry little weight for the Bonferroni-corrected entire data set. For those few individual parameters that do not match, we can invoke the caveat mentioned in Principle 10, and reasonably anticipate that more extensive sampling of the quarry would eliminate these anomalies.

The primary rock-forming and accessory mineral assemblages, Pl + Aug ± Ol + Hbl + Bt + Ti - Mag + Ap + Zrn (Whitney and Evans 2010), of the Baxter headstone, Ritcey headstone, and Hanson quarry are identical. A haplogabbro contains augite as its sole ferromagnesian phase, so that these three gabbros contain four primary ferromagnesian phases (Ol + Aug + Hbl + Bt) is sufficiently unusual to be important in establishing a match. What is also important is that some of the other “black granite” quarries in the Saint George Batholith contain prominent primary titanite, a feature of their mineral assemblages that may serve to exclude them as possible sources for the Titanic headstones (Table 7).

Once the primary mineral assemblage is established, additional similarity depends on the modal proportions of each phase. That all Titanic headstone and Hanson quarry samples are common gabbros, as opposed to, say, troctolites or norites or anorthosites, is essential but not particularly useful in making the case for a match. Additionally, the modal proportion of olivine in the Titanic headstones and Hanson quarry ranges from 0–1%, unlike some of the other gabbro quarries in southwestern New Brunswick (e.g., Spinney), which consistently have much higher modal abundances of olivine.

The textural fingerprint of an igneous rock involves a unique combination of grain sizes, grain shapes, grain orientations, and relationships among grains. All Titanic headstone and Hanson quarry samples are uniformly medium-grained (1–5 mm). The most striking macroscopic textural feature of all these gabbros is the random orientation of the euhedral plagioclase laths (“snowflake” texture; Holt 2000) (Fig. 1b).

At the microscopic level, all Titanic headstone and Hanson quarry rocks have a cumulate texture, with cumulus grains of olivine, plagioclase, and titaniferous magnetite, and large intercumulus grains of augite (Fig. 8a). Furthermore, the corroded anhedral olivine is poikilitically enclosed in augite (Fig. 8b). Although many moderately potassic olivine-bearing gabbros contain prominent apatite prisms, the Titanic headstone and Hanson quarry samples all contain fine-grained anhedral apatite, located along grain boundaries or as inclusions in plagioclase (Fig. 8c, d). Finally, the cumulus titaniferous magnetite grains in all samples commonly have irregular composite reaction rims of hornblende and biotite (Fig. 8e).

The secondary alteration minerals, muscovite + chlorite + actinolite, are identical in the headstone and quarry populations, and only the degree of alteration varies somewhat from one sample to another. Furthermore, the degree of alteration in other candidate quarries varies widely from fresh (Spinney) to strongly altered (Townsend), rendering them unsuitable matches for the Titanic headstones on the basis of their degree of alteration alone.

Muscovite alteration of plagioclase and chlorite alteration of ferromagnesian minerals in all headstone and quarry samples is unremarkable, but the distinctive partial replacement of augite by actinolite (Fig. 8f) is more unusual, and strengthens the ties between the Titanic headstones and Hanson quarry.

In this section, we have presented and compared primary mineral assemblages, secondary mineral assemblages, primary textures, and secondary textures in the Titanic headstones and Hanson quarry. Although there are no statistical tests, according to Principles 3 and 9, the greater the number of qualitative parameters shared by the Titanic headstones and Hanson quarry, the greater is the probability that they are the same rock.

From approximately 1870 to 1940, St. George, New Brunswick, had a reputation as “The Granite Town”. At its peak of production, as many as six companies, cutting and polishing dimension stone, operated along the banks of the Magaguadavic River (Martin 2013). As many as 50 quarries intermittently supplied a wide variety of red, pink, and grey granite, as well as “black granite” (gabbro), to these monument companies. An examination of the obituaries in the St. Croix Courier, the St. Andrews Beacon, and the Granite Town Greetings shows a mortality rate in surrounding Charlotte County on the order of one person per day, meaning a local demand for about 180 headstones in a six-month period. If, against this level of demand, came an order from the White Star Line for an additional 150 headstones over a similar six-month period, the source quarry and monument company (or companies) needed to have access to enough material, and have the manufacturing capacity, to be able to accommodate this sudden increase in demand. On the question of availability of material, a rough estimate shows that the total volume of the Titanic headstones constitutes only about 1% of the excavated volume of the Charles Hanson quarry. On the question of manufacturing capacity, the simple standard chisel shapes of most of the Titanic headstones (Fig. 1), and polishing of only two surfaces (top and front), speaks either to economy (the White Star Line was infamously parsimonious) or haste (delivery of the headstones to Halifax began six months after the Titanic sank), or both.

According to Principle 7, any gabbro quarry operating during, or before, 1912 is a possible source for the Titanic headstones, whereas any quarry that opened after 1912 is not possible. If the historical record of operation is correct, at least five of the fourteen truly gabbroic quarries did not exist in 1912 (Table 7). With respect to the Charles Hanson quarry specifically, “The owners of the black granite quarry at Bocabec will commence the construction of their works as soon as the necessary arrangements can be made.” (St. Croix Courier, January 11, 1894). In 1906, Henry McGrattan & Sons took over operation of the “black granite” quarry in Bocabec and built a scow to transport rock to St. George. A year later, the company was actively promoting this material: “Due respect for our departed loved ones demands that we erect not only Artistic but Enduring Memorials. … Granite is everlasting and our Egyptian Black Granite is far more Artistic and Expressive than any other granite.” (Advertisement in Granite Town Greetings, December 4, 1907). Holt (2000) recorded the following: “Down over the Hill, just near Hiram Hanson and beside Bocabec River, was an Agricultural Hall where Fairs were held. My great aunt took me there in the fall of 1893. … Across the Upper Bocabec Bridge, a road led to a granite quarry on land belonging to Charles, son of Hiram Hanson. This quarry was operating in 1908–1909 (I’m sure of this). Another black granite was on the Sam  Orr property in lower Bocabec. The Black granite is all over this part of Bocabec.” Thus, the Hanson quarry appears to have been well established, and its products actively marketed as Egyptian Black, before 1912.

All gabbro quarries had transportation routes of various degrees of difficulty to St. George, some overland, some by inland lakes and rivers, and others by sea. According to Principle 8, all other factors being equal, an actively operating gabbro quarry with the easiest transportation route to St. George might be the most likely to have supplied the Titanic headstone material. Table 7 also shows the straight-line distance of each quarry to St. George, and whether that route was primarily by land or by water. Given the primitive state of roads in 1912, water routes were logistically easier than land routes, and saltwater routes more reliable yearround than freshwater routes. These sorts of considerations make the Hanson and Chickahominy quarries highly probable sources for the Titanic headstone material. The transportation logistics criterion is, however, only relative, because all those quarries did send dimension stone to St. George at one time or another, regardless of the difficulty.

The Great Southern Railway began service to St. George in 1882. In 1889, the Great Southern became the Shoreline Railroad, and in 1911 it became part of the Canadian Pacific Railroad. Connections east to Moncton, and south to Halifax on the Intercolonial Railway, later to become Canadian National Railways, also were in operation at this time, and this transportation corridor would have made for quick and easy shipment of dimension stone from St. George to Halifax. In this case, it would not be surprising to also find true granite headstones from the Saint George Batholith in Halifax cemeteries. The Mount Olivet Cemetery in Halifax appears to contain gabbros from the Saint George Batholith (in addition to the 19 Titanic headstones that are already there), and a wider survey of Halifax cemeteries may show even more dimension stone with sources in southwestern New Brunswick.

Sometime in 1913, the year following the sinking of the Titanic, and after at least the initial delivery of the headstones to Halifax, John McGrattan, operator of the Charles Hanson quarry in Bocabec, donated a marker (Fig. 9a) to the New Brunswick Museum in Saint John (inscribed as H. McGrattan & Sons, and catalogued as NBME 1103). Although we have no petrographic, geochemical, or geochronological data for this stone, this marker is a good macroscopic textural match for the Titanic headstones (Fig. 9b). The McGrattan marker also bears a striking morphological and textural resemblance to the generic “Mother” and “Father” markers in the Rural Cemetery in St. Stephen. The question is: why did John McGrattan donate this particular specimen to the New Brunswick Museum and at this particular time? Presumably it was not a common occurrence for quarry operators to donate samples of their products to the Museum. Two possible answers are that this specimen may have been part of a display of New Brunswick dimension stones for participants in an International Geological Congress field trip to the Museum in 1913, or that it was a sample of the Titanic headstones, or both. Future forensic petrological work may yet link the McGrattan marker to the Charles Hanson quarry.

At the turn of the 20^th Century, St. George had a wellearned reputation as “The Granite Town”, supplied by many quarries. In 1912, the operationally and logistically easiest of the “black granite” quarries was the Charles Hanson quarry. The monument works in St. George had the capacity to handle a large order in a relatively short period of time, and also had a well-established rail network to more distant markets. All these circumstantial lines of evidence point to St. George in general, and/or the Charles Hanson quarry in particular, as a reasonable source of the Titanic headstones in Halifax. Although the enigmatic H. McGrattan & Sons marker in the New Brunswick Museum may be an intriguing clue linking the headstones and the Charles Hanson quarry, what is critically missing is any historical document to support the many lines of scientific and circumstantial evidence.

Table 8 illustrates how each of the four essential and diagnostic characteristics of the Titanic headstones served to reduce the search area for the source quarry. Principle 2 helped to locate the geological region of Maine and southwestern New Brunswick, Principle 5 narrowed the search to southwestern New Brunswick, and Principle 6 helped to locate the possible source quarries. The probabilities in the final column conservatively assume: that all ages from 0 to 4 Ga are equally represented in the continental crust of the Earth; that gabbros constitute 5% of continental crust; that 1% of all 422 Ma gabbros have textures that match the Titanic headstones; and that 1% of all gabbros with ages, mineralogy, and texture matching the Titanic headstones would also have matching chemical compositions for most elements. If so, the probability that the Titanic headstones and Hanson quarry have so many similar properties, but are completely unrelated, is 1 in 100 million. In fact, the true probability is much less, because we have not included the olivine and augite mineral compositions. In this regard, the highly variable (even in the lithologically restricted range of gabbros) parameters of the age, mineral assemblage, texture, whole-rock chemical composition, and mineral composition are as effective as human DNA in making genetic connections, in this case between the Titanic headstones in Halifax and the Hanson quarry in Bocabec.

According to Principle 1, we cannot know the original coordinates of the headstones in their three-dimensional source quarry, because the headstones have been removed and their former location is now marked by a lithological void. Given this condition, one of four scenarios must apply (Fig. 10):

1. if the source quarry is perfectly homogeneous on a scale larger than the quarry, the headstones, and any other loose quarried blocks, will perfectly match the physical, chemical, and temporal parameters of the quarry walls and floor;

2. if the source quarry is monotonically variable with horizontal isopleths, the physical and chemical parameters of the headstones will be bounded by these parameters in the walls of the quarry, perhaps even perfectly matched in the walls and loose quarried blocks, and the ages will match precisely;

3. if the source quarry is monotonically variable with vertical isopleths, the physical and chemical parameters of the headstones will be bounded by these parameters in the floor of the quarry, perhaps even perfectly matched in the floor and loose quarried blocks, and the ages will match precisely;

4. if the source quarry is irregularly variable, the physical and chemical parameters of the headstones might not match some, or even any, of these parameters in the walls and floor of the quarry, and may match some loose quarried blocks, but the ages will match precisely.

For virtually every quantitative parameter [zircon age, olivine FeO/(FeO + MgO) values, augite rim compositions, whole-rock major- and trace-element compositions], we have been able to show that the Titanic headstones and Hanson quarry values are not statistically different, thus an approximation to conditions (2) and (3) above holds, i.e., there is chemical variation in the walls, floor, and blocks of the quarry that almost entirely captures the mineralogical and lithological chemical variation in the headstones. The diagram showing chemical variation for olivine grains (Fig. 5b), as well as the box plots for augite grains (Figs. 6c, d), clearly illustrate this concept. For almost every chemical parameter, at least some overlap exists between the composition of the Titanic headstones and the compositions of material from the quarry.

Of the several scenarios depicted in Figure 10, the case of chemical homogeneity in the quarry and headstones clearly does not apply (Fig. 10a), nor does the case of an absence of compositional overlap between quarry and headstones (Fig. 10d). It is not possible to know precisely where in the spectrum from horizontal to vertical isopleths the Hanson quarry lies, but this scenario would seem to apply to the case of the Titanic headstones, with a major caveat. Figure 10d shows the condition in which the walls and floor of the source quarry have no compositional overlap with dimension stone removed from it. This is a low-probability situation, but it is not impossible. Conversely, it is possible that a perfect compositional match between a given quarry and a given dimension stone does not necessarily mean a source-derivative relationship between them. It might mean, however improbably, that another quarry exists with the same matching properties.

In summary, a perfect match between quarry and dimension stone does not necessarily mean a genetic connection, and a perfect mismatch does not necessarily mean the lack of a genetic connection. The statistically good match between Hanson and Titanic leaves open the possibility that another unknown and unnamed quarry exists that is the source of the Titanic headstones. However, of the three types of “black granite” quarries in southwestern New Brunswick, namely known and named, known and unnamed, unknown and unnamed, which type is the most likely to be the source of the Titanic headstones? We invoke Ockham’s razor, the law of parsimony, to conclude that a known and named quarry, in this case the Charles Hanson quarry, is more likely to have supplied the large quantity of material for the Titanic headstones than any hypothetical, equally or even better matching, unknown and unnamed quarry.

Several steps could be taken to further test our hypothesis:

1. use a portable XRF instrument to expand our knowledge of the chemical composition of the Titanic headstones;

2. find a dimension stone that was known for certain to have been sold as “Egyptian Black”, and compare it with the Hanson quarry to confirm our deduction that Hanson is the right source quarry for the Titanic headstones;

3. locate the elusive “lower” quarry at Chickahominy and the “black granite” on the Sam Orr property (Holt 2000), because it is still possible for another quarry to be a better match;

4. look farther afield to quarries in Memramcook and Welsford to improve confidence

5. use textural comparisons and a portable XRF instrument to compare the McGrattan marker with the Titanic headstones;

6. add chemical analyses from the other “black granite” quarries in Table 5;

7. continue the search for archival documentation to provide historical confirmation of the scientific assessment.