Dirrington Great Law is a hill in the Scottish Borders

Scottish Borders

The Scottish Borders is one of 32 local government council areas of Scotland. It is bordered by Dumfries and Galloway in the west, South Lanarkshire and West Lothian in the north west, City of Edinburgh, East Lothian, Midlothian to the north; and the non-metropolitan counties of Northumberland...

 area of Scotland

Scotland

Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

, in the former county of Berwickshire

Berwickshire

Berwickshire or the County of Berwick is a registration county, a committee area of the Scottish Borders Council, and a lieutenancy area of Scotland, on the border with England. The town after which it is named—Berwick-upon-Tweed—was lost by Scotland to England in 1482...

. The summit is around 2.5 kilometres (1.6 mi) south of Longformacus

Longformacus

Longformacus is a small village in Berwickshire in the Scottish Borders area of Scotland. It is around north-west of Duns, in the Lammermuir Hills. The Dye Water runs through the village, flowing east towards its confluence with the Whiteadder Water nearby...

 and 9 kilometres (5.6 mi) west of Duns

Duns

Duns is the county town of the historic county of Berwickshire, within the Scottish Borders.-Early history:Duns law, the original site of the town of Duns, has the remains of an Iron Age hillfort at its summit...

. It is an isolated hill to the south of the Lammermuir Plateau

Lammermuir Hills

The Lammermuir Hills, usually simply called the Lammermuirs , in southern Scotland, form a natural boundary between Lothian and the Scottish Borders....

. Dirrington Little Law (360 metres (1,181.1 ft)) is located 2 kilometres (1.2 mi) to the south-west.

Geologically, the two Dirrington Laws comprise Carboniferous

Carboniferous

The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...

 volcanic felsite

Felsite

Felsite is a very fine grained volcanic rock that may or may not contain larger crystals. Felsite is a field term for a light colored rock that typically requires petrographic examination or chemical analysis for more precise definition...

 (riebeckite

Riebeckite

Riebeckite is a sodium-rich member of the amphibole group of silicate minerals, chemical formula [][Na2][32][2|Si8O22]. It forms a series with magnesioriebeckite. It crystallizes in the monoclinic system, usually as long prismatic crystals showing a diamond-shaped cross section, but also in...

), and may be the remains of a laccolith

Laccolith

A laccolith is a sheet intrusion that has been injected between two layers of sedimentary rock. The pressure of the magma is high enough that the overlying strata are forced upward, giving the laccolith a dome or mushroom-like form with a generally planar base.Laccoliths tend to form at relatively...

, a type of volcanic intrusion

Intrusion

An intrusion is liquid rock that forms under Earth's surface. Magma from under the surface is slowly pushed up from deep within the earth into any cracks or spaces it can find, sometimes pushing existing country rock out of the way, a process that can take millions of years. As the rock slowly...

 into the surrounding sedimentary rocks of the Old Red Sandstone

Old Red Sandstone

The Old Red Sandstone is a British rock formation of considerable importance to early paleontology. For convenience the short version of the term, 'ORS' is often used in literature on the subject.-Sedimentology:...

.

At the summit of Dirrington Great Law are three large circular cairns, 23.5 metres (77.1 ft), 21 metres (68.9 ft), and 8.5 metres (27.9 ft) in diameter. The cairns are composed of stones excavated from the hilltop, rather than from loose stone gathered from the ground.