It sounds like you might be describing a type of marble or a similar stone, possibly used for countertops, flooring, or wall cladding. The intense, deep grey background with mesh-like pale veins is typical of some varieties of marble, which are celebrated for their beauty and elegance. The veins not only add contrast but also enhance the depth and character of the stone, making each slab unique. The glossy sheen mentioned could refer to the polished finish often applied to marble to accentuate its natural patterns and shine. If you need more details or want information on how to use, maintain, or procure such a material, feel free to ask!