We find this material throughout Ayrshire but this piece of quartz crystal came from a rock hunt in the last week of February, from near Alloway. 
This is how agates form in the rock, they are chipped out of the bubbles in the host material. In this case it appears to be basalt. The basalt is iron Stained a lovely deep wine red and greenish on the bottom. 
This is a really heavy rock, indicating that it might be more than just basalt. A lapidary artist could cut it open to find out. We like it as a quartz crystal specimen for any crystal collection.