On Wednesday evening, the incident occurred near Limekiln Road in Abersychan, Torfaen.
According to Gwent Police, the Pontypool boy died at the scene.
The girl from Blaenavon was rescued from the quarry by a Coastguard helicopter, and she is now being treated at the University Hospital of Wales in Cardiff.
According to one councillor, the incident would reverberate throughout the local communities.
On Wednesday evening, a 14-year-old girl was flown to the hospital by helicopter.
At 6.30 p.m., the Welsh Ambulance Service received a 999 call, and South Wales Fire and Rescue Service dispatched two crews to the scene.
The Welsh Ambulance Service requested assistance from HM Coastguard at 7.20 p.m. due to the nature of the terrain at the quarry, according to HM Coastguard.
According to a spokeswoman, the coastguard helicopter was dispatched from its base in St Athan, and a paramedic was winched down to rescue one of the casualties.
She was then flown to a heliport in Cardiff before being transported by ambulance to the University Hospital of Wales.
A 15-year-old boy died after falling into an Abersychan quarry.
Torfaen council said it was working closely with the boy’s school’s leadership team to provide support for everyone affected.
“Our colleagues from the educational psychology service have been at the school since the beginning of the day,” it said, adding that “further support is also available from the school counselling service.”
It went on to say that the land is privately owned.
The Reverend John Edward Funnell of Abersychan’s Noddfa Church said he was “so proud” of how the valley has come together.
“We got a lot of messages last night when we saw helicopters flying through the valley.” “We were all very concerned about what had occurred,” he explained.
Reverend John Edward Funnell said the community’s support has been wonderful. “This morning the community has rallied together, it’s been wonderful to support each other,” he added.
“The local school has been fantastic, as have the emergency services.” “I’m so proud of how our valley has banded together during this difficult time.”
“This is a tragic incident, and the effects will reverberate throughout the communities of Blaenavon and Abersychan,” said Councillor Janet Jones, who represents Blaenavon.
“My thoughts are with the two families, and I’m confident that the local community and community council will come together to support them during this difficult time.”
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