Dragon heartstring is a material from a dragon that can be used in the core of a wand. It is unknown from which varieties of dragon the heartstrings are collected, and what effect this difference makes on the abilities of the wand, if any. Due to the heart being a vital organ in any creature, it can be assumed that the material is taken after the dragon has either died of natural causes or been killed. It is also unknown what quantity of string can be collected from each beast's heart.
As a rule, dragon heartstrings produce wands with the most power, capable of the most flamboyant spells. Dragon wands tend to learn quicker than other types. While they can change allegiance if won from their original master, they always bond strongly with the current owner.
The dragon wand tends to be easiest to turn to the Dark Arts, though it will not incline that way of its own accord. It is also the most prone of the three cores to accidents, being somewhat temperamental. It also tends to be lethally hazardous if combined with certain woods. 
Usage by wandmakers
The wandmaker Garrick Ollivander is known to use dragon heartstrings as one of his three cores; the others being unicorn hairs and phoenix feathers. Gregorovitch also used dragon heartstring in his wands, such as the one he made for Viktor Krum.
The following wands have a dragon heartstring core:
- Hermione Granger's wand
- Viktor Krum's wand
- Bellatrix Lestrange's wand
- Gilderoy Lockhart's wand
- Lucius Malfoy's wand
- Minerva McGonagall's wand
- Garrick Ollivander's wand
- Peter Pettigrew's wand
- Dolores Umbridge's wand
- Horace Slughorn's wand
- Harry Potter and the Goblet of Fire (First mentioned)
- Harry Potter and the Deathly Hallows (Mentioned only)
- Harry Potter and the Deathly Hallows: Part 1 (Mentioned only)
- Harry Potter and the Deathly Hallows: Part 2 (Mentioned only)
- Pottermore (Mentioned only)
Notes and references
- ↑ 1.0 1.1 http://lady-slytherin-forever.tumblr.com/post/8977640199/wand-cores-off-of-pottermore New wand core information from pottermore