Black Onyx is believed to be one of the most powerful protection
stones. Its way of protecting is to absorb and transform
negative energy. Because of this quality. people find it
helpful in relieving stress and for emotional stability.
It's one of the first (root chakra) grounding stones; as
such, it encourages connection to material goals and to
determination in realizing them.
In much crystal literature Black Onyx is strongly associated
to Saturn, and it is said that this stone works most positively
for those with a strong Saturn in their natal charts. Although
this may include people born under the sign of Capricorn,
it's not limited to them.
The above is mentioned because it's part of the lore about
this stone; however, Black Onyx has another characteristic
which can make it valuable to anyone.
It has been said that in India it was commonly worn to cool
the ardour's of love. It may be very helpful for people
who can't let go of past relationships (sometimes even long
after they're over.)
The same can be true of any belief which no longer serves
one - and they can be as hard to let go of as past relationships.
Onyx can help to bring us into contact with our actual realities,
and assist us in gradually releasing all that is not in
harmony with our present lives.