Basalt is a deep, inky near-black, and the worst thing you can do with it is treat it like a feature wall. It comes alive when you drench the room — walls, woodwork, ceiling, the lot — so it reads as one continuous envelope rather than a dark slab fighting against bright trim.
Once you've committed to that, the job is putting warmth and light back in by way of materials and accents, not by hacking the colour scheme apart. Brass, aged bronze, marble, timber and pools of lamp or candlelight do the heavy lifting here.
For those warm metallic moments, Dulux Copper Glow (LRV 30.1) is a cracking partner — a burnished, coppery tone that echoes brass hardware and picks up beautifully under warm lighting. If you want a paint that deepens rather than lightens — say for a built-in, a hallway runner of colour, or a connecting space — Mylands Cigar BH.20 (LRV 11.8) is a rich, smoky brown that sits in the same low-light register as Basalt without going flat.
When you do need something pale — ceiling in an adjoining room, trim in a brighter space next door, or soft furnishings — go warm, never stark. Paint & Paper Library Sand I (LRV 95.4) is a gentle, creamy off-white that flatters Basalt's depth. Farrow & Ball All White (LRV 92) works too if you want something cleaner but still without the cold blue cast of a brilliant white.
The "but what about a bit of contrast?" question always comes up. My honest answer: resist it. A brilliant white skirting against Basalt looks like an unfinished job, not a design choice. If you crave relief, let texture and metal provide it.
Practical tip — order a sample pot and paint a large piece of lining paper, then live with it morning and night. Basalt swallows light, so a north-facing room needs proper layered lighting (table lamps, picture lights) to stop it feeling cave-like. Get the lighting sorted first and the colour will sing.