Shivaling has three distinct parts which are considered as portions of Brahma, Vishnu and Shiva. The lower part represents Brahma, the middle Vishnu and the upper and the most prominent represents Shiva. Thus, Shivling represents all the three powers in one- as the Param Braham or Supreme Shiva.
Another interpretation considers Shivling to be divided in two parts Shiva and Shakti. The top part is considered Shiva and the yoni is considered to be Shakti.
Shivaling made up of crystal have special significance. Such Shivaling have no colour of its own but it takes the colour of any object that comes in its contact. The ling as such represents the attribute-less and formless supreme Shiva.
There is mysterious and indescribable power in Shivaling to induce the concentration of mind. It is like the crystal glazing, mind easily attains one-pointedness by looking at the Shivaling. This is the reason why ancient scholars and sages advocated the worship of Shivaling and its installations in temples.
As per Ramayana "Lord Rama and Lord Laxman sat on a crystal rock". Sphatik carries the properties of prosperity, happiness and brings harmony to the house where it is worshipped. Crystal helps in gaining a better understanding of our instinctual powers. Sphatik idols are considered highly auspicious for puja
Purpose: Sphatik idols remove any negative energies in the area, it is kept. Worshiping of a Shivalinga made of sphatik is considered to have the same effect as worshiping the "Jyotirlings".