What exactly is Black Basalt Rock Dust?
A finely ground volcanic rock amendment (olivine-rich basalt) that adds slow-release minerals—especially silica, calcium and magnesium—plus iron, potassium and trace elements. It also gently lifts acidic soils toward neutral, improving nutrient availability.
What’s the typical mineral analysis?
Approx. pH 8.5; Silica 43%; Calcium 7%; Magnesium 14%; Potassium 1.7%; Iron 14%; Manganese 0.2%.
How does Black Basalt Rock Dust help plants—what will I actually notice?
Stronger cell walls from silica (sturdier stems, better stress tolerance), better enzyme function and chlorophyll production from Mg and Fe (richer green), improved fruit/flower quality, and steadier overall growth as soils get remineralised.
Does Black Basalt Rock Dust raise soil pH?
Yes—basalt dust is mildly liming. It’s great for acidic soils, peat-based mixes and areas with high rainfall. Avoid heavy use if your soil is already alkaline.
Can Black Basalt Rock Dust replace garden lime?
It can lift pH, but it’s slower and more nutrient-dense than straight lime. If you need a fast pH correction, use ag-lime; use basalt to build minerals and maintain pH over time.
For a broader look at pH targets, nutrient lockout and the role of mineral amendments in living soil, see our living soil pH basics guide.
How much should I use in garden beds or lawns?
General topdress: ~100 g per m². Work it into the top few centimetres and water in. For lawns, the same 100 g per m² at the start of the growing season works well.
What’s the dose for potting mixes?
Mix 50–80 g per 30 L of potting soil. For fresh blends, aim for ~5–10% of your normal fertiliser routine by weight.
How often should I reapply?
Apply at the start of each season. Minerals release slowly, so little-and-often beats a one-off dump.
Is Black Basalt Rock Dust good for coco coir?
Yes. Coco is naturally short on calcium and magnesium—this product helps buffer and stabilise coco mixes.
Will Black Basalt Rock Dust fix acidic peat moss?
Yep. It nudges peat-based mixes into a more plant-friendly range while adding trace minerals.
Can I use Black Basalt Rock Dust in a worm farm or compost?
Absolutely. A light dusting in worm bins and compost improves mineral content and helps worms grind food. Don’t overdo it—think “pinch of salt,” not a thick layer.
Safe for native Aussie plants?
Many natives prefer slightly acidic soils, so go light (well under 100 g per m²) and monitor pH. If your natives sulk in alkaline soils, skip it around them.
Will Black Basalt Rock Dust help with fruiting and flowering plants?
Yes. Remineralised soils support better blossom set, flavour and shelf life. Pair it with your usual balanced nutrition—basalt isn’t a complete fertiliser by itself.
Is Black Basalt Rock Dust okay for raised beds?
Yes—just measure. Raised beds can swing pH faster, so stick near 100 g per m² and check pH every few months.
If you're using mineral amendments as part of a wider soil-building plan, see our guide to bringing tired garden soil back to life.
Can I topdress established plants?
Sprinkle lightly around the dripline, scratch in, and water. It doesn’t need to be buried deep to work.
How long until I see results?
Some users notice greener growth within a few weeks; the full soil-building benefits accrue over seasons as minerals weather in.
Does Black Basalt Rock Dust add phosphorus?
Basalt is low in P. It shines for silica, Ca, Mg, Fe and trace elements—use a separate P source if a soil test shows you’re low.
Can I use Black Basalt Rock Dust with organic fertilisers and microbes?
Yes. It plays nicely with compost, manures, worm castings, mycorrhizae and biologicals. Microbes help unlock the minerals faster.
For a broader look at mineral amendments alongside plant- and biology-based inputs, see our animal-free fertiliser guide for Australian gardens.
Hydroponics—yay or nay?
Nay. It’s a soil/soilless media amendment, not for recirculating hydro systems.
Will Black Basalt Rock Dust create salt build-up or burn roots?
No—there’s no synthetic salt load and it’s very gentle. Just stay within the recommended rates.
Any heavy-metal concerns?
Basalt typically has very low problematic metals compared with some “mystery” rock powders. As with any mineral dust, use the directed rates and keep it out of ponds.
What’s the particle size—does Black Basalt Rock Dust dust up?
It’s a fine powder for faster weathering, so it can be dusty. Apply on a still day, wear a dust mask, and lightly water after spreading.
Can I use Black Basalt Rock Dust as a foliar spray?
No—it’s not soluble. Keep it to soil/medium applications.
What’s the best way to combine Black Basalt Rock Dust in a new mix?
Blend evenly through the media (50–80 g per 30 L), add your compost/organic fertiliser, moisten, and let it sit a few days before planting if you can.
Is Black Basalt Rock Dust okay for seedlings?
Yes in small amounts mixed through the medium. Avoid heavy topdressing on tiny seedlings.
Will Black Basalt Rock Dust help in high-rainfall or leached sandy soils?
Definitely. It helps rebuild cation balance (Ca/Mg/K), improves structure over time, and counters acidification.
Does Black Basalt Rock Dust sequester carbon?
Basalt weathering binds atmospheric CO₂ as stable carbonates in soils. Think of it as a slow, soil-first climate positive.
Can Black Basalt Rock Dust improve disease or stress tolerance?
Silica-rich soils tend to produce tougher plants with better resistance to abiotic stress (heat, drought, wind) and some pest/disease pressure.
What should I NOT mix Black Basalt Rock Dust with?
There’s no hard incompatibility, but if you’re liming heavily already, reduce either the lime or the basalt to avoid overshooting pH.
Storage and shelf life?
Store sealed, cool and dry. It can cake if it absorbs moisture—just crumble it up before use. Minerals don’t “expire.”
What sizes are available?
1 kg, 2.5 kg and 5 kg resealable bags.
Is the packaging resealable?
Yes—heavy-duty, resealable bags for cleaner storage and easy dosing.
Any quick recipe ideas?
• Potting mix booster: per 30 L—50–80 g basalt + quality compost + a balanced organic fertiliser. • Lawn lift: 100 g/m² brushed in after mowing, water well. • Coco buffer: 1–2 tbsp per 10 L of hydrated coco, mix thoroughly.
Bottom line—when should I choose Black Basalt Rock Dust over other rock dusts?
When you want a broad mineral profile with a strong calcium/magnesium punch, gentle pH lift for acidic media, and a proven, slow-release way to build soil health without messing with your fertiliser program.
