Lithium, beryllium and boron are rare because although they are produced by nuclear fusion, they are destroyed by other fusion reactions in the stars. This pro

Lithium, beryllium and boron are rare because although they are produced by nuclear fusion, they are destroyed by other fusion reactions in the stars. This property is used to distinguish low mass stars and brown dwarfs. https://en.wikipedia.org/wiki/Lithium_burning https://en.wikipedia.org/wiki/Lithium_burning https://en.wikipedia.org/wiki/Cosmological_lithium_problem#Observed_abundance_of_lithium https://en.wikipedia.org/wiki/Cosmological_lithium_problem#O...