A deel an item of traditional clothing commonly worn since centuries ago among the Mogols. The deel looks like a large overcoat when not worn. Instead of buttoning together in the middle, the sides are pulled against the wearer's body, the right flap close to the body with the left covering. On the right side of the wearer are typically 5 or 6 clasps to hold the top flap in place. There is one clasp below the armpit, three at the shoulder, and either one or two at the neckline.
For men, the deel for work is traditionally made of thick cotton or wool, while the women's deel is more luxurious, with silk prints. Winter deels are covered with sheep or goat skin. The traditional hat can be made of fur, silk, or felt according to its shape. The boots are generally made of leather with a thick felt lining. Many herders make their own deel and boots, and wear them, but more and more Mongolians wear occidental clothes. Nowadays, most city-wellers wear the Mongolian traditional costume only for celebrations like Tsagaan Sar or for special occasions like graduation ceremony or weddings.
From the beginning of the 20th century, women started to wear a sophisticated and richly decorated deel, with beautiful jewels, to show their social position. For example, the deel of a Khalkh girl (the largest subgroup of Mongolpeople) was made with silk and brocade covered with gold or silver. On top of it, she could choose to wear a uuj, or a dress without sleeves of a different colour. Regarding jewels, she used to wear pendants in coral, jade, pearls, or other precious stones, pearls being considered as the most precious material, coral and silver after. Hair were most often flattened and tied in a high veil decorated with silver.
According to en.wikipedia and Horseback Mongolia