Boron is a typical non-metal.

Aluminium is a metal but shows many chemical similarities to boron. While gallium, indium, thallium and nihonium are almost exclusively metallic in character.

Boron is a fairly rare element, it mainly occurs as orthoboric acid $\left(\mathrm{H}_{3} \mathrm{BO}_{3}\right)$, borax $\left(\mathrm{Na}_{2} \mathrm{~B}_{4} \mathrm{O}_{7} \cdot 10 \mathrm{H}_{2} \mathrm{O}\right)$ and kernite $\left(\mathrm{Na}_{2} \mathrm{~B}_{4} \mathrm{O}_{7} \cdot 4 \mathrm{H}_{2} \mathrm{O}\right)$.

In India borax occurs in Puga Valley (Ladakh) and Sambhar Lake (Rajasthan). The abundance of boron in earth crust is less than $0.0001 \%$ by mass.

There are two isotopic forms of boron ${ }^{10} \mathrm{~B}(19 \%)$ and ${ }^{11} \mathrm{~B}(81 \%)$.

Aluminium is the most abundant metal and the third most abundant element in the earth's crust ($8.3\%$ by mass) after oxygen ($45.5\%$) and $Si$ ($27.7\%$).

Bauxite $\left(\mathrm{Al}_{2} \mathrm{O}_{3} \cdot 2 \mathrm{H}_{2} \mathrm{O}\right)$ and cryolite $\left(\mathrm{Na}_{3} \mathrm{AlF}_{6}\right)$ are the important minerals of aluminium. In India it is found as mica in Madhya Pradesh, Karnataka, Orissa and Jammu.

Gallium, indium and thallium are less abundant elements in nature.