A Rudraksha Tree at Rishikesh
Fruit on the Tree
Rudraksha (Sanskrit: rudrākṣa) ("Rudra-eyed") is the name of the dark berries of Elaeocarpus ganitrus, used to make prayer beads (Sanskrit: mālā). William Roxburgh ( June 29, 1751 &ndash April 10, 1815) was a Scottish Surgeon and Botanist. Elaeocarpus is a Genus of tropical and subtropical Evergreen trees and shrubs  The word is a Sanskrit compound consisting of the name Rudra and ākṣa ("eye"). Sanskrit (sa संस्कृता वाक् saṃskṛtā vāk, for short sa संस्कृतम् saṃskṛtam) is a historical Rudra ( Sanskrit: रुद्रः is a Rigvedic god of the storm the wind and the hunt
The Rudraksha is a large evergreen broad-leaved tree that grows in the area from the Gangetic Plain to the foothills of the Himalayas. The Indo-Gangetic Plain also known as the Northern plains and the North Indian River Plain is a large and fertile plain encompassing most of northern and eastern India, Rudraksha trees are also found in middle areas of Nepal. Rudraksha seeds are covered by an outer shell of blue color when fully ripe, and for this reason are also known as blueberry beads. A seed (in some plants referred to as a kernel) is a small embryonic Plant enclosed in a covering called the seed coat usually with some stored Blueberries are Flowering plants in the genus Vaccinium, sect The blue colour is derived not from pigment but is structural. 
Rudraksha beads are the material from which sacred garlands (108 beads in number) or rosaries are made. A bead is a small decorative object that is pierced for threading or stringing The Rosary (from Latin rosarium, meaning "rose garden" or "garland of roses" is a popular traditional Roman Catholic devotion. The term is used both for the berries themselves and as a term for the type of mālā made from them. A Japa mala or mala (Sanskritsa माला mālā meaning Garland) is a set of Beads commonly used by Hindus and Buddhists  In this sense, a rudraksha is a Saivite rosary, used for japa mala. Shaivism, also spelled "Saivism" names the oldest of the four sects of Hinduism. The Rosary (from Latin rosarium, meaning "rose garden" or "garland of roses" is a popular traditional Roman Catholic devotion. A Japa mala or mala (Sanskritsa माला mālā meaning Garland) is a set of Beads commonly used by Hindus and Buddhists Repetitive prayer (japa) is a common aid to worship in Hinduism, and Rudraksha mālā are worn by many Hindus. Japa ( Sanskrit: जप is a Spiritual discipline involving the meditative repetition of a Mantra or name of God. Hinduism is a religious tradition that originated in the Indian subcontinent. Rudraksha is also used for treatment of various diseases in traditional Indian medicine. India, officially the Republic of India (भारत गणराज्य inc-Latn Bhārat Gaṇarājya; see also other Indian languages) is a country
The berries show variation in the number of grooves on their surface, and are classified on the basis of the number of divisions that they have. A common type has five divisions, and these are considered to be symbolic of the five faces of Shiva. 
The Rudraksh seeds are brittle in nature and so should be protected from chemicals.
The best way to find the authenticity of a rudraksha is to get it X-rayed and count the number of compartments inside. If they are equal to the number of lines outside the rudraksha is real.