The Shiva Linga or Lingam is a symbol that represents Lord Shiva in Hinduism. Here is a hand carved SIVA LINGA symbol, it appears likely carved out of black marble, or onyx.  Excellent undamaged condition, see all photos.

4.5" tall, 5" across

FROM THE INTERNET: 

Shiva, as the most powerful of deities, temples are built in his honor that includes a Shiva Linga, representing all the energies of the world and beyond. 

Innovatively designed and crafted Marble Shivling offered by us are widely praised. Fabricated from unmatched grade marble these Shivling Statues are very appealing in look and are very easy to maintain also. Amazing colors combination of these Marble Shivling easily catche the eye of art lover.A marble shivling is considered highly auspicious and is said to have one of the highest frequency vibration rate. Shivling is considered to be good luck and praying to shivling is considered to be bowing to Lord shiva directly.

It is believed that during "Ramayan Kaal" Lord Ram and Laxman sat on the sphatik rock. The most common use of the Shiva Lingam is for sacred bathing (abhishekam) and so the worship of a Shiva Lingam always includes an abhisheka usually of milk and water.