It brings mental organization and is very grounding and calming. It helps with original thinking, logical thinking, and mathematics.

Hematite is associated with the root (base) chakra. 

  Hematite is good at grounding out excess energy and acting as a stabilizing force.

Metaphysical and healing properties of Aventurine crystals

Aventurine (Green)
Aventurine is said to benefit one in all areas of creativity, and imagination, as well as intellect and mental clarity. Lore says that it enhances prosperity and brings career success. It is a gentle stone energetically that gives a sense of calm and balance and enhances happiness. It also helps one to see alternatives and potentials in all situations, giving a positive outlook, courage and inner strength. It is also said to bring luck, especially in games of chance. Green aventurine is also a mystical stone of prosperity. Aventurine bring friendship to one's life. It is also a stone of protection energies. Folklore and metaphysical lore say that physically it is beneficial for blood, circulatory system, headaches, general health, and sleep disorders.

Aventurine is associated with the heart chakra.

taken from "The Crystal Bible" by Judy Hall and the superb site Crystal and Jewelry