'had burnt' is correct and usable in written English.
You can use it as part of the past perfect tense. For example, "The house had burnt down before anyone had a chance to extinguish the fire".
It was like a last leap of the flame that had burnt clear and high four years before.
Vivienne Eliot always insisted there was a lost fifth quartet, Chipping Norton, which was TSE's masterpiece and that Valerie had burnt it (hence the reference to Burnt Norton).
The hole in the rug that Mian Tajammul Hussain's cigarette had burnt 40 or 45 years earlier remained, except that it had grown so large that now you could pass a watermelon through it.
Three of the sites had not been burnt since 1975 and acted as controls, with covers of pine trees, shrubs, and annual vegetation; three sites had burnt only in 2012 and contained burnt pines but no shrubs or annual vegetation; and three degraded sites had suffered from three wildfires prior to 2012 and contained no vegetation.
All of their limbs had burnt away.
The general feeling was that Nirvana had burnt out.
The Nazis had burnt and banned children's books.
Many had burnt their fingers on speculative towers in the 1990s.
There was also significant bolstering of the mental health workforce, which had burnt out by 2006.
We learned later that the place we'd just played had burnt down the following night.
She claimed that her stepfather had burnt her hand with a butt and touched her privates.
