As asked in a couple of emails already, there are many crystals that may be helpful for dealing with the horror and pain of the Boston Marathon bombing today, or any other tragedy.
Root chakra stones (list near bottom of page) such as schorl, red jasper, black onyx and others can stabilize you in the here and now. Most of us are not actually there at any given tragic incident, though our hearts bleed for those who are. Staying rooted in the moment can help cope with high emotions whether you are affected by being present at a tragedy or dealing with it from a distance.
For the emotional trauma of tragedy, bloodstone, rhodonite, rose quartz, and citrine can be helpful. Crystals used for PTSD such as lepidolite, richterite, and jade may also be helpful in preventing full blown PTSD. Calming stones such as lepidolite again, or blue calcite, hematite, red calcite, lithium quartz, and others can also be helpful emotionally.
Quartz crystals are wonderful for sending powerful healing energies to all involved, as well as good wishes and positive energy..
For sending highest and best Divine wishes for those affected directly, smoky quartz and rainbow moonstone would be good choices. Angel stones like angelite, celestite and seraphinite would also be excellent choices.
Any or all of these stones can be used in crystal gridding, crystal meditations, as an adjunct to healing prayer, distance Reiki, or other energy work.