Calcium Carbonate (precipitated chalk) increases pH; 1 gram per gallon adds 106 ppm calcium, 158 ppm carbonate.
Works as should.disolves quickly.
Well, if you need to use calcium carbonate to adjust your water chemistry, you can use this without issue.
I live in Seattle. The water that comes out of the tap is essentially rain water. I like to brew English ales and Continental lagers so add calcium carbonate and / or salts and / or gypsum to my mash water on every batch.