How do elements of group 13 occur in nature?

(a) Occurence of boron and uses:
Boron is not found free in nature. It mainly occurs as bortes and orthoboric acid. The important minerals of boron are:
1. Borax (Tincal) Na₂B₄O₇ . 10H₂O
2. Colemanite Ca₂B₆O₁₁ . 5H₂O
3. Kernite Na₂B₄O₇.2H₂O
4. Boric acid H₃BO₃
In India borax occurs in Puga valley (Ladakh) and Sambhar Lake (Rajasthan). The abundance of boron in the earth crust is less than 0.0001% by mass. There are two isotopic forms of boron ^l0B(19%) and ¹¹B(81 %).
(b) Occurrence of aluminium and uses:
Aluminium does not occur freely in nature, but its compounds (minerals) are widely distributed in nature. It is the third most abundant element (next to oxygen and silicon). Some minerals of aluminium are
1. Oxides.
(i) Corundum (Al₂O₃)
(ii) Diaspore (Al₂O₃H₂O)
(iii) Bauxite (Al₂O₃.2H₂O)

2. Fluoride, Cryolite Na₃AlF₆

3. Silicate.
(i) Feldspar (KA1 Si₃O₈)
(ii) Kaolin or slate (K₂O.2H₂O.3Al₂O₃.6SiO₂)
4. Basic sulphate Alunite or Alum stone K₂SO₄ Al₂(SO₄)₃.4Al(OH)₃
The important ore of aluminium is bauxite. In India aluminium is found as mica in Madhya Pradesh, Karnataka, Orissa and Jammu.

(c) Occurrence of gallium, indium and thallium These are less abundant elements in nature.