*4.2. Fracture Pattern in Støypet Valley Chromite Layers*

The fracture pattern in chromite layers interbedded with dunite is characteristic of basement rocks exposed in the valley floor (Figure 3) and south wall of Støypet valley near its opening to the northeast (Figure 7a). In closer view (Figure 7b), the pattern of vertical joints seen in two dimensions defines columns roughly 40 cm wide. The resulting fractures in combination with horizontal layering results in a two-dimensional outline of rectangular shapes. A set of measurements in two dimensions is represented by a small sample from the outcrop surface. The larger rectangle defined by fractures at the center of Figure 7b is 33 × 21 cm. Smaller rectangles in the layer directly above measure 16 × 9 cm and 11.5 × 10 cm, respectively. Not shown in its entirety (Figure 7b), a much larger rectangle at the side has a height of at least 43 cm. This general pattern would have been subject to hydraulic pressure and plucking during wave impact in the early Holocene when Støypet valley was first flooded. Initially, any blocks so removed from chromite sea cliffs would have been rectilinear in three dimensions prior to the rounding of cobbles and small boulders that resulted from clast abrasion. The size range of cobbles and small boulders in the boulder beach at the top of Støypet (Figure 5a) readily fit with this pattern of fracture-size and shapes. Calculations for 80% of volume from a three-dimensional cubic solution (Appendix A and Tables A1–A3) is a rough estimate for the size reduction of individual cobbles and boulders that underwent abrasion after removal from sea cliffs during contact with one another under storm conditions.

**Figure 7.** Natural fracture pattern in chromite layers interbedded with dunite exposed in the south wall of Støypet valley: (**a**) view to the south at the northeast end of Støypet valley showing chromite layers approximately 4 m thick and (**b**) close-up view showing vertical joints spaced about 40 cm apart.

#### *4.3. Chromite Ore Density*

The sample of low-grade chromite ore collected at Støypet yielded a value of 3.32 g/cm<sup>3</sup> for density based on a small cobble weighing 83 gm and displacing an equivalent volume of water amounting to 25 m. The number is derived by dividing weight by volume. This value was applied uniformly to all clasts listed in Tables A1–A3.
