Smoky Quartz is helpful for those with cancer as it draws negative energies out of the body. Smoky Quartz is also known for its strong ability to absorb and ground negative energies out of the body, and into the earth to be transmuted. These properties make Smoky Quartz a great support crystal for those undergoing chemo and radiation therapies. 
As a healing stone, Smoky Quartz aids in the proper functioning of the adrenals, the kidneys and the pancreas. It has a relaxing effect, helping to block negativity, and aiding in meditation. It also helps develop ones latent abilities as a Channel, or Medium.
Smoky Quartz stimulates and purifies the base Chakra and stimulates the movement of Kundalini Energy by channeling the white light energy of the Crown Chakra into the First Chakra.
It is believed to help one come to terms with their own circumstances, becoming more acceptant of their own bodies and lives. It helps us to make our dreams into reality. It stimulates pride, self respect and self esteem. 
Smoky Quartz is especially useful for grounding and draining away negative energy.

 

The most important property of citrine is that it dissipates negative energies of all kinds and does not absorb any negative energy from its surroundings, and thus never needs clearing/cleansing. 
Citrine can be used to clear unwanted energies from the environment. Family issues caused by negative energies can also be resolved and cleared with citrine. Since citrine eliminates negative energies, it helps generate stability in all areas, and is good for general protection.

In the mental area, citrine enhances mental clarity, confidence, and will power. It also increases creativity and promotes honesty.

Emotionally, citrine relieves depression, self-doubt, anger, and irrational mood swings. Citrine is a stone that brings happiness and cheer to one who carries or wears it. Citrine also reduces self-destructive tendencies. Citrine helps eliminate fears caused by others' ideas and suggestions. It can help one overcome emotional traumas and grief. Sensuality and sexuality can also be heightened by citrine.

In the psychic and spiritual realms, citrine is good for general psychic awareness and spiritual development. Citrine clears the aura of negative energies and influences. It is also very useful for meditation. Citrine is a stone of protection, removing or deflecting negative energies of all kinds. It is also excellent for dream recall and dream work.
Physically, in crystal healing and folklore, citrine is said to be beneficial for the digestion, stomach, eliminating nightmares and other sleep disturbances, thyroid, general health, heart, kidney, liver, muscles, strength, endocrine system, circulatory system, tissue regeneration, urinary system, immune system, diabetes, fibromyalgia. Citrine is also reputed to be good for removing toxins, and overcoming addictions.