• Volcanic Rock Dust — pile of fine grey-green basalt powder
  • Volcanic Rock Dust — 200g kraft resealable pouch with dr forest label, Extra fine powder
  • Volcanic Rock Dust — back of kraft pouch with Directions for Use panel
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Dr Forest

Volcanic Rock Dust UK | Micronised Basalt | 70+ Minerals

Volcanic Rock Dust UK | Micronised Basalt | 70+ Minerals

£5.99 GBP
£5.99 GBP
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  • ✓Made with organic ingredients, no slaughterhouse by-products

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Looking for the granulated version for lawns and top-dressing? → Granulated Rock Dust

Micronised volcanic rock dust — ultra-fine basalt for foliar spray, root drench, fertigation & compost tea

Micronised Powder Fastest Release pH 11 — Lime Alternative Compost Tea Ready 48% Silica OF&G Organic

Modern gardens and allotments are consistently over-supplied with nitrogen, phosphorus, and potassium — and chronically deficient in the trace minerals that make everything else work. Plants cannot manufacture minerals; they can only extract what is present in the soil. Once a mineral is depleted by cropping and not replaced, it is gone. This volcanic rock dust powder is the fastest-acting form available: micronised to ultra-fine particle size, it presents the maximum reactive surface area to soil water, producing plant-available silicic acid and releasing its full mineral spectrum significantly faster than granulated rock dust. The fine particle size also lets it suspend in water, so it can be applied as a foliar spray, root drench or through fertigation — the fastest route to making basalt's trace minerals plant-available.

This powder is produced from Vulkamin — a zeolite-rich silicate of volcanic origin with pH 11. Micronising multiplies its effective surface area many times over compared with granulated material: the same weight of rock delivers a far greater immediate weathering response. This makes the powder the preferred format for compost teas, potting media blending, and situations where faster results are needed. It is also the most efficient format for broadcast application to beds where it can be raked into the soil and begin weathering immediately on contact with soil moisture.

At pH 11, this powder also functions as a gentle, long-lasting alternative to agricultural lime for correcting acid soils — raising pH progressively without the risk of overliming, while simultaneously supplying the trace minerals, silica, and zeolites that lime does not provide.

pH 11Acidity Corrector
20%Yield Increase (Sheffield)
4×CO₂ Stored vs Untreated
52%Tomato Yield (Trial)

What micronised volcanic rock dust is used for

  • Compost tea mineral enrichment — the fine powder suspends in aerated brews, delivering a full trace mineral spectrum directly to roots and foliage alongside the microbial benefits of the tea; minerals are chelated by fulvic acid in the brew for immediate plant availability
  • Potting media blending — mix directly into compost at potting time for instant mineral enrichment of the growing medium; far more effective than granules, which weather too slowly to benefit plants during a single container season
  • Fastest soil remineralisation — rake into the top 5–10 cm of beds at planting time; the fine particles begin weathering immediately on contact with soil moisture, producing silicic acid and releasing trace elements faster than any granulated product
  • Silicon delivery for pest and disease resistance — silicic acid strengthens cell walls, increases resistance to aphids, whitefly, spider mites, and fungal pathogens; trials eliminated botrytis in strawberries without any chemical input
  • Soil pH correction — lime alternative — at pH 11, Vulkamin raises and maintains soil pH progressively; gentler and longer-lasting than lime, with no overliming risk, while supplying trace minerals and silica that lime cannot
  • Fruit quality, Brix and flavour improvement — remineralised plants produce firmer, more flavourful fruit with measurably higher nutrient and sugar density; trial data shows 52% tomato yield increase with improved Brix
  • Carbon sequestration through enhanced weathering — as silicate minerals dissolve in soil water they react with CO₂ to form stable bicarbonate minerals; University of Sheffield research found basalt-treated soils stored 2–4 tonnes CO₂/ha over five years
  • Compost heap activation — dust between layers to enrich finished compost with the full mineral spectrum and feed composting micro-organisms; the heat and acidity in an active heap accelerates weathering dramatically

Micronised powder vs granulated rock dust — which to use

Micronised Powder (this product)

  • Ultra-fine particle size — maximum surface area for fastest mineral release
  • Minerals become plant-available within weeks rather than months
  • Suspends in water — the only format suitable for compost tea and liquid applications
  • Most effective format for potting media where minerals must release within a single growing season
  • pH 11 — effective lime alternative for acid soil correction
  • Greater CO₂ sequestration rate due to faster enhanced weathering
  • Fine and dusty — wear a mask when handling in enclosed spaces

Dr Forest Granulated Volcanic Rock Dust

  • Coarser granular form — designed for sustained release over months to years
  • Less dusty and easier to handle for broadcast top dressing
  • Ideal for lawns, open beds, and large-area application without dust
  • Provides a long-term mineral reservoir that persists in soil for years
  • Cannot be used in compost tea or liquid applications
  • The better choice for long-term soil building where speed is not critical
  • Use both together: micronised for the fast hit, granules for the sustained reserve

The science of micronised basalt: weathering, silicon, zeolites & enhanced carbon capture

What Vulkamin is and why particle size matters

Vulkamin is produced from volcanic lava that solidified before reaching the Earth's surface — and therefore never oxidised. This sub-volcanic origin preserves its zeolite mineral content intact. Zeolites form when volcanic glass is slowly altered by water over millions of years, producing aluminosilicate minerals with a unique open crystalline lattice. This structure gives Vulkamin exceptional surface area, moisture absorption, and the ability to exchange mineral ions with soil solution over a prolonged period.

Micronising amplifies all of these properties. A finer powder presents more surface area to soil water per gram, accelerating silicic acid production, pH buffering, and trace mineral release. It also suspends in water readily — making the powder the only format suitable for compost tea and liquid drench applications. The same weight of micronised powder weathers many times faster than the equivalent weight of granulated material.

The silicon mechanism — how basalt protects plants

  • Silicon cannot be absorbed in its mineral form — basalt must first weather to produce soluble silicic acid (H₄SiO₄)
  • Micronised powder produces silicic acid faster than granulated material due to its far greater surface area
  • Once inside the plant, silicon is deposited in cell walls and epidermal tissue as opaline silica
  • This creates a physical barrier against fungal hyphae — strawberry trials eliminated botrytis without fungicide
  • Silicified stems support heavier fruit and flower loads without lodging or bending
  • Reduces water loss through leaves under drought stress
  • Maintains deeper leaf colour and higher photosynthetic rate
  • Directly improves Brix (sugar density) through enhanced photosynthesis and mineral uptake

Enhanced weathering — how basalt sequesters carbon

  • As silicate minerals dissolve in soil water they react with dissolved CO₂ to form stable bicarbonate minerals
  • This permanently removes atmospheric carbon — the bicarbonates are geologically stable for thousands of years
  • Finer particle size accelerates this process — micronised powder sequesters carbon faster than granulated material
  • University of Sheffield research (Kelland et al. 2020) found basalt-treated soils stored 2–4 tonnes CO₂/ha over five years — four times more than untreated soil
  • Simultaneously corrects soil acidity through the same weathering reaction — reducing the need for agricultural lime
  • Every application of micronised rock dust is a direct contribution to carbon removal from the atmosphere

Published trial results

01

Sorghum — University of Sheffield

Up to 20% yield increase without phosphate or potassium fertilisers. Soils stored 2–4 tonnes CO₂ per hectare over five years — four times more than untreated controls. Soil acidification was mitigated without lime application. Published: Kelland et al. (2020), Global Change Biology.

02

Spring Oats — UK Field Trial (UNDO / Newcastle University)

Average 15% yield increase in the first year. Elevated soil pH without lime. Higher calcium, potassium, and grain mineral content. No toxic element uptake detected in treated crops. Published: UNDO / Newcastle University (2024), Farming Future Food.

03

Tomato — Greenhouse Trial

52% yield increase over untreated control. Higher Brix (sugar content). Increased iron and calcium in harvested fruit. Cascade Minerals greenhouse trial (2015).

04

Strawberry — 25-Year Study

Botrytis completely eliminated without fungicide over 25 years of basalt application. Fruit consistently firm, ripe, and disease-free. Extended shelf life. Significantly larger root systems than fertiliser-only controls. Leipold (1980–2005), reported by Remineralize the Earth.

05

Maize & Bean — Geoderma Regional

Macro and micronutrient accumulations up to five times higher than untreated controls. Improved vegetative growth and nutritional status across both crops. Pereira et al. (2022), Geoderma Regional.

Scientific References

  1. Kelland, M.E. et al. (2020). Increased yield and CO₂ sequestration potential with basalt rock dust. Global Change Biology, 26(6), 3658–3676.
  2. UNDO & Newcastle University (2024). Nafferton Farm volcanic rock dust trial. Farming Future Food.
  3. Cascade Minerals (2015). Greenhouse tomato trial: 52% yield increase.
  4. Leipold, F. (1980–2005). 25-year basalt trials. Remineralize the Earth (2007).
  5. Pereira, E.G. et al. (2022). Potential of basalt dust to improve soil fertility and crop nutrition. Geoderma Regional, 31, e00579.
  6. Beerling, D.J. et al. (2018). Farming with crops and rocks. Nature Plants, 4, 138–147.
  7. Epstein, E. (1999). Silicon. Annual Review of Plant Physiology, 50, 641–664.

How to use micronised volcanic rock dust: compost tea, soil application & rates

Dust precaution

The micronised powder is very fine and will become airborne in dry, windy conditions. Apply on calm days or when soil is moist. Wear a dust mask when handling in enclosed spaces such as polytunnels or glasshouses. Outdoors in normal conditions no mask is required for typical garden quantities.

Method 1 — Compost tea mineral enrichment

Adding Vulkamin powder to an actively aerated compost tea brew introduces a broad trace mineral spectrum alongside the microbial content of the tea. The fine particles suspend in the aerated liquid and the minerals are partially chelated by the fulvic and humic acids produced during brewing, making them immediately plant-available.

  1. Prepare your compost tea as normal. Fill your brew vessel with dechlorinated water, add compost or worm castings in a mesh bag, and start your air pump and airstone. Begin aeration before adding the rock dust.
  2. Add Vulkamin powder at 1–2g per litre of brew volume. For a 20-litre bucket, add 20–40g. The agitation from the airstone keeps the fine particles in suspension throughout the brew.
  3. Brew for the normal period — 24–48 hours. Keep the air pump running throughout. The rock dust remains suspended during active aeration. Minerals are progressively chelated by organic acids produced during the brew.
  4. Apply immediately after brewing. Use within 4 hours of switching off the pump. Stir well before applying to redistribute any settled particles. Apply as a soil drench or foliar spray (filter through 200 micron mesh for fine spray nozzles).
Compost tea rate reference

Vulkamin powder in compost tea: 1–2g per litre of brew. For a standard 20-litre bucket, add 20–40g. For an enhanced mineral drench, add Dr Forest Fulvic Acid Powder at 1–2g/L to the finished tea before application — the fulvic acid chelates the volcanic minerals into immediately plant-available form.

Method 2 — Soil broadcast and incorporation

Vegetable beds and borders — maintenance

Rate: 100g per m² | Frequency: Spring and/or autumn

Scatter over moist soil surface and rake into the top 5 cm immediately to prevent wind dispersal. Water in well. The fine particles begin weathering immediately on contact with soil moisture.

New or depleted beds — first application

Rate: 200–300g per m² | Frequency: Once, before first planting

Incorporate into the top 15–20 cm thoroughly before planting. Higher rate for soils that have never received rock dust or that are known to be mineral-depleted. The fine particles begin producing silicic acid and releasing trace minerals within days of incorporation into moist soil.

Containers and potting media

Rate: 5g per litre of compost (approx. 1 teaspoon/L) | Frequency: Once at potting

Mix thoroughly into compost before planting. Far more effective than granulated rock dust in containers — the fine particles weather within a single growing season, releasing their full mineral spectrum while the plant is actively growing. Critical for peat-free and coir-based media which contain very little native mineral content.

Compost heap activation

Rate: Light dusting between layers | Frequency: Each time you add material

Dust between green and brown layers as you build or turn the heap. The heat, moisture, and microbial acidity within an active compost heap weathers the fine particles dramatically faster than open soil — enriching the finished compost with the full basalt mineral spectrum.

Acid soil pH correction — lime alternative

Rate: 200–400g per m² | Frequency: Annually until target pH is reached

At pH 11, Vulkamin raises soil pH progressively through the same enhanced weathering reaction that releases its minerals. Apply 200–400g/m² annually and test soil pH each spring. The pH correction is gentler and longer-lasting than lime, with no overliming risk. Simultaneously supplies trace minerals and silica that lime does not provide. Expect pH to rise by approximately 0.3–0.5 units per growing season at the higher application rate, depending on starting pH and soil type.

A note on timescales

Even micronised powder works through mineral weathering rather than instant solubility — this is not a liquid fertiliser. The finer particle size means faster results than granulated material, but the full mineral benefit still builds over one or more growing seasons. Most growers notice silicon-driven improvements — reduced disease incidence, improved stem strength, better fruit firmness — within the first season. Mineral reserve accumulation compounds over successive annual applications.

Works well combined with…

Volcanic rock dust supplies minerals; it does not replace nitrogen or fast-acting nutrition. Combine with a base granular fertiliser — the All-Purpose 6-6-6 or a crop-specific blend. Adding Fulvic Acid Powder to compost tea applications significantly amplifies mineral uptake — the fulvic acid chelates volcanic minerals for immediate root absorption. For long-term soil building, combine with Humic Acid Granules as a monthly soil drench and Granulated Volcanic Rock Dust for the slow-release reservoir. Use Grow-Kashi to inoculate the biology that weathers rock particles fastest.

Frequently asked questions about micronised volcanic rock dust

The powder delivers faster mineral release due to its far greater surface area per gram. It is the right choice when you need faster results, when you want to use it in compost tea or liquid applications, or when mixing into potting compost where minerals must release within a single growing season. The granulated version is better for long-term open-ground top dressing without dust risk. Ideally, use both: the micronised for the fast hit, the granules for the sustained reserve.
Yes. At pH 11, Vulkamin raises soil pH progressively through the same enhanced weathering reaction that releases its minerals. It is gentler and longer-lasting than lime, with no overliming risk. Apply 200–400g/m² annually and test soil pH each spring. Unlike lime, it simultaneously supplies trace minerals, silica, and zeolites — correcting acidity while remineralising the soil at the same time. Expect pH to rise approximately 0.3–0.5 units per season at the higher rate.
Yes — Vulkamin is microbe-friendly. Its zeolite pore structure actually provides physical habitat for beneficial bacteria, and the trace minerals it releases are cofactors for microbial enzyme activity. The pH 11 of the dry powder becomes negligible at the 1–2g/L rates used in compost tea — the buffering capacity of the brew water and organic acids maintains a healthy pH for microbial life throughout the brew. Add 20–40g per 20-litre brew.
For soil drenches applied with a watering can, no issues at all. For foliar sprayers with fine nozzles, filter through a fine mesh (200 micron or finer) before filling the sprayer. The very fine particles mostly pass through mesh filters, but straining gives extra insurance for precision equipment. Do not use undiluted powder suspensions in drip irrigation emitters — apply as a soil drench around plants instead.
No — it supplies trace minerals and silicon that fertilisers do not contain. Use it alongside a good fertiliser programme, not instead of one. The minerals it provides are the cofactors that allow plants to use NPK more efficiently — enzyme construction, vitamin synthesis, amino acid building, and the structural silicon that supports growth under stress. Plants fed with both a fertiliser programme and regular rock dust consistently outperform those on fertiliser alone.
Silicon-driven improvements — reduced disease incidence, improved stem strength, better fruit firmness — are typically visible within one growing season. The powder acts faster than granulated material due to its greater surface area, so silicic acid production begins more quickly after application. Mineral reserve accumulation continues to build over successive annual applications, compounding the benefits year on year.
Yes. This is 100% natural volcanic rock with no synthetic chemistry. It is approved for certified organic production with no withholding period for edible crops. University of Sheffield and Newcastle University trials specifically confirmed no toxic element uptake by crops grown in basalt-treated soil. Once incorporated into soil, the garden is safe for pets and children as normal. Avoid inhaling the powder in quantity — basic dust precautions apply during handling.
Store in the original sealed bag or an airtight container in a cool, dry place. The fine powder is hygroscopic and will absorb moisture and clump if the bag is left open — clumping does not affect efficacy but makes accurate measuring harder. Reseal immediately after each use. Shelf life is effectively indefinite when stored dry — rock minerals do not degrade over time.
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