Howlite is an extremely calming stone. It is an excellent antidote to insomnia especially when this is caused by an overactive mind.  It links into the spiritual dimensions, opening attunement and preparing the mind to receive wisdom and insights.   Amber is strictly speaking not a crystal. It is tree resin that solidified and became fossilised. It has strong connections with the earth and is a grounding stone for higher energies.*
* Judy Hall "The Crystal Bible" 2009