Dragon's egg explained

A dragon's egg is a fireworks pyrotechnic star^[1] which first burns for a period for a visual effect and then loudly deflagrates.^[2] This effect became controversial because of the toxic compounds once used, particularly lead tetroxide (Pb₃O₄). ^[3]

Bismuth trioxide or bismuth subcarbonate are commonly used as more environmentally friendly substitutes for lead compounds to achieve the effect, and its occurrence in fireworks displays has since become much more common.

Because of how heavy an individual bismuth atom is, a shell or cake containing mainly dragon's eggs (and therefore enriched in bismuth) is often noticeably heavier than a similar device containing other effects.

Further reading

• 10.1016/j.atmosenv.2010.05.048 . Emission factors and exposures from ground-level pyrotechnics . 2010 . Croteau . Gerry . Dills . Russell . Beaudreau . Marc . Davis . Mac . Atmospheric Environment . 44 . 27 . 3295. 2010AtmEn..44.3295C .
• Book: The Preparatory Manual of Black Powder and Pyrotechnics . 9781411685741 . Ledgard . Jared . 2006-02-22. Lulu Press, Incorporated .

Notes and References

1. Book: Linda D. Hall. Brands and Their Companies: Consumer Products and Their Manufacturers with Addresses and Phone Numbers. 2006. Thomson Gale. 978-0-7876-8951-3.
2. Web site: Firework Effect - Dragon Eggs . October 20, 2000 . youtube.com . video.
3. Book: Chris Mocella. John A. Conkling. Chemistry of Pyrotechnics: Basic Principles and Theory, Third Edition. 15 January 2019. CRC Press. 978-1-351-62655-2. 51–.