The quarry site is currently characterized by a mix of partially submerged and buried pits, standing ruins, and surviving remnants of its industrial infrastructure.

The pits vary in their current condition: the Twll Mawr and Twll Balast pits are partially filled with water and spoil, while the Hen Dwll pit, located on the eastern side, is now largely covered beneath tipping from the adjacent Pen y Orsedd quarry.

Despite its closure, the site retains many industrial and historic features. The older southern area contains the ruins of several buildings, some of which may date back to the 18th century, in addition to the much older 15th-century Pen y Bryn farm. In the newer northern mills area, surviving structures include the walls of a long mill building, a barracks, and the chimney of a winding house.

Infrastructure remains are also evident across the site. Formations of various inclines are present, along with a drum house that still contains some of its gear. Other surviving artefacts include flat rods and traces of a bucket pump. Several tunnels that once provided access to the upper pits are still open. The quarry’s connection to the Nantlle Railway is visible through the formations of both its original and diverted routes, with some of the original stone blocks remaining in place. Additionally, tramway formations are still present, including the abutments of a bridge used to run spoil onto the Dorothea property.

Upper Pit adits

Middle Adit

Middle adit, located on same level as main dressing floor, is open, and is in good condition apart from a collapse right at the entrance. The adit has slate slabs for walking, but rail and sleepers have been removed apart from the odd bit of rail and fastenings. The adit terminates at a precipitous drop overlooking the pit. The adit can be seen continuing into the opposite quarry wall on what must have been an exploratory drive prior to digging the pit.

Lower Adit

Located just north east of the Twll Mawr pit at the point where the Pen y Bryn tips are about to inundate it. Collapsed a short distance inside.

Starting around 1770, the quarry’s main period of operation concluded in the late 1890s, though minor work persisted until the 1940s. Post-World War II, the Dorothea Company attempted a revival by building a road, but this effort failed.

At its peak in 1882, the operation was significant, employing 240 men and yielding 5,083 tons of slate. The quarry was laid out with four pits linked by a central mill area. Pumping and winding power evolved over time; initially, two waterwheels provided pumping power, which was later replaced by steam power for both pumping and winding. The site was known for being an early adopter of new technology, including the use of chain inclines starting around 1830, and later supplementing these with Blondin cable cranes, which were used until the late 1930s.

Transport involved an unusual incline with a buried drum that descended to the Nantlle Railway. The railway originally ended here before its eventual extension to Pen yr Orsedd. As the quarry expanded, the Nantlle Railway was diverted southward, and this older route is still traceable today. After 1836, the quarry came under the control of the Dorothea company, which utilized a section of the site for tipping spoil.