Slate is a fine-grainted, metamorphoic rock
Slate is a fine-grainted, metamorphoic rock
Two types of quarrying occurred on the Boston Harbor Islands—cutting bedrock outcrops that are present on some islands for building materials and removing sand, gravel, and stones from islands for ships’ ballast. To discuss the former first, most of the bedrock under the Harbor Islands is argillite, a metamorphic slate (conglomerate, the other type of island bedrock, occurs only on islands in Hingham Bay) and it was argillite that was quarried. On the eponymous Slate Island, for example, in 1631 the government forbade the removal of slate without permission, but in 1650, when it granted the island to an individual, said anyone could gather slate. In the 19th century, quarries on the northwest side of the island provided slate used for building foundations and cellars (Sweetser 1988 [1888]:210–11). Slate was quarried on Hangman Island in the late 17th century when the quarry rights were owned by a Mrs. Olive Smallpiece (Snow 1971:120). Arthur W. Austin established a quarry on Outer Brewster perhaps in 1843 and the slate and diabase (not granite, as many sources mistakenly report) from it were reportedly used to build two stone houses in Charlestown—92 Main Street (1822) and a half house on the Harvard Mall (c. 1800)—as well as to macadamize some Boston roads (Sweetser 1988 [1888]:249; Snow 1971:247–48. Note that there are some discrepancies here of dates that need further research, especially since the stone houses in Charlestown were reportedly built by Nathaniel Austin, Arthur’s father.) And it was reportedly the quarrying of slate on Nixes Mate that caused that island to erode from a sheep pasture in the 17th and 18th centuries to the present shoal (Sweetser 1988 [1888]:197).

Removing ballast from the Harbor Islands—the second type of quarrying—may have begun in the 17th century or even earlier, but is well documented in the 19th, when the city became concerned about erosion of the islands, which were thought to protect the harbor. As early as 1818 the state required a license be obtained from the Boston selectmen to remove “earth and stones” from Bird Island, which even by 1794 had eroded to such an extent that it was only above water at low tide (Boston City Document 1853:27–28; Pemberton 1794:295). This law was apparently not well enforced, for in 1827, when Mayor Josiah Quincy was trying to obtain legislation and appropriations to protect the Harbor Islands against erosion, he mentioned the continuing practice of taking ballast and sand from Bird Island as well as from the sand spit extending southwest from Great Brewster (Quincy 1852:119). Quincy’s efforts to prevent erosion of the Harbor Islands also included references to taking ballast from Georges and Lovells. He said that in 1823, for example, the sale of stone and gravel from those islands had contributed to the fact that half of Georges had eroded away (Quincy 1852:117).
Failed seawall on Great Brewster; quarries produced ballast and stone for seawalls
Failed seawall on Great Brewster; quarries produced ballast and stone for seawalls
Taking ballast from the islands continued in the mid-19th century. An 1846 report of the Boston Marine Society stated that 62,000 tons of stone and gravel were taken annually from the Harbor Islands—30,000 from Great Brewster and the sand spit, 20,000 from Long, 10,000 from Gallops, and 2,000 from Deer (Boston City Document 1853:17). The next year the city petitioned the state legislature for an act prohibiting the taking of sand or gravel from Gallops or Great Brewster, but the owner of the latter protested that it would infringe on his property rights and the act was not passed (Boston City Document 1853:21). Similar problems beset later efforts to stop the removal of ballast from Long and Gallops. In 1852 it was reported that the U.S. Government’s attempts to purchase Long Island Head in order to erect a seawall there had failed because the owners received considerable income from the sale of ballast and were thus asking an unreasonable price. And although removing ballast from Gallops had caused it to erode, forming a spit at its northeast point, the owner was also asking a very high price to compensate for the income he would lose if not selling ballast (Boston City Document 1853:25–26). In 1860, a federal commission appointed to study the deterioration of Boston Harbor was still concerned about this spit on the east end of Gallops that had been caused by removing ballast (Boston City Document 1860:5). Removal of ballast from the Harbor Islands continued to be a problem. An 1856 illustration in Ballou’s Pictorial shows taking ballast from Long, and Stark recorded that a “considerable” part of Slate Island was removed for ballast in the 1870s (Stark 1879:133).

What remains…
Evidence of the quarrying that took place on some islands is still visible. On Outer Brewster, for example, there is stone debris on the ground and the canal that the Austins cut partially through the east end of the island in order to create a protected anchorage. The house foundation located on the island by a 1974 archaeological survey (Luedtke 1975:86) may also have been associated with this quarry. Evidence of the 19th-century quarrying on Slate is also still apparent (Klein 2008:128) but it is not known whether any remains of the 17th-century quarrying on that island are still visible.

Prepared by Nancy S. Seaholes, 2009


Last updated: February 26, 2015

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