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.

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.

 

Opal amplifies traits, whether those traits are good or bad, and brings characteristics to the surface for transformation. It enhances self worth, confidence and self-esteem, and helps you to understand your full potential. It also brings lightness and spontaneity. The stone is said to help stimulate originality and dynamic creativity, encourages an interest in the arts, and aids in accessing one’s true self. Because the stone is absorbent and reflective, it helps you to pick up thoughts and feelings, amplify them, and return them to their source. It is a karmic stone- it encourages putting out positive emotions and teaches that what you put out comes back to you. The opal is also a representative of justice and harmony, and is a protective stone in dangerous places.
Opal has always been associated with love and passion, as well as desire and eroticism. It is a seductive stone that intensifies emotional states and releases inhibitions. It can also act as an emotional stabilizer. Wearing an opal is said to bring about loyalty and faithfulness.
Opals have been said to be extremely beneficial in many physical realms as well, such as in treating infections and fevers. It is also said to help strengthen the memory. Furthermore, it purifying blood and kidneys, regulates insulin, eases childbirth, and alleviates PMS. It is also beneficial to the eyes, especially as an elixir. Overall, the stone is said to be the most useful in preventing bad health. It strengthens the immune system and helps the body be resilient to infection.
Opal has also been known to help those who are suffering from chemical dependencies. The stone gives the wearer strength and the ability to take back control over their lives.