Boron is a metalloid, exhibiting characteristics of both metals and non-metals. It is never found in its pure form in Earth, but it is a component of some minerals. However, pure boron can form as a result of chemical reactions. It can be a brown amorphous solid, or a crystalline solid. In the crystalline form, it is black and very hard. Its chemical properties are mostly, but not entirely, non-metallic. Like non-metallic compounds it doesnt react with water.
So, in pure mineral form and under normal conditions it doesn't react with water.