It's clear the beskar is extremely resilient and largely impervious to blaster bolts.
How resistant is beskar to a direct attack from a lightsaber?
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Spoiler for Season 2 Episode 5 of The Mandalorian
We finally got to see beskar go up against a lightsaber in live action. And it can indeed deflect a saber's blows. In fact it holds up better than I thought it would. There are a few instances where they make prolonged contact for several seconds with no visible signs of damage. It doesn't even heat up the metal to any noticeable degree.
It's upper limits are still unknown. But it's safe to say that beskar is very resistant to a lightsaber's attacks.
Mandalorian armor is known as beskar’gam (iron skin) in the Mandalorian language, and is worn exclusively by warriors. It is worn by both men and women, and while it gives excellent protection, it also creates a common appearance regardless of species or gender.
The highest quality sets are made by lightsaber-resistant beskar (Mandalorian Iron), but the exceptionally high cost and rarity of beskar has led to the use of durasteel, alum, and duraplast in armor production.
Mandalorian metalsmiths have traditionally kepth the methods for working beskar into an alloy a highly guarded secret, but the element could be mixed with other metals such as ciridium to create a highly dense and almost indestructible set of armor.
Also from the canon page of SW Fandom:
Beskar was one of the toughest and most legendary metals in the galaxy. The alloy could withstand direct blaster fire and was capable of repelling the strikes of a lightsaber. The metal could also be reforged to any warrior's liking.
(Star Wars Rebels: Heroes of Mandalore animated series)