Diatomite is a sedimentary rock composed largely or wholly of the siliceous skeletal remains of microscopic, mainly aquatic plants called diatoms that are a type of algae. The skeletons (frustules) consist of amorphous (as opposed to crystalline), opaline or hydrous silica, but the rock may be contaminated by varying amounts of organic matter, alumina, iron, soluble salts, and sedimentary particles such as clay, carbonates, and sand.
Mt Sylvia Diatomite is a massive near white relatively pure diatomite, although the colour becomes darker with increasing content of organic matter. It has a chalky appearance and is generally soft and friable.
The mass packing of individual diatoms results in a microscopically porous material of low density and high bulk. It has the ability to absorb up to 200% of its own weight in water. The diatomite particles are polarized and when the diatomite is added to soils it has the added benefit of keeping the soil pores open, allowing easy penetration of water and oxygen.
Diatomite also neutralizes toxic components that may be present in the soil such as aluminium and heavy metals. It is the most soluble form of pure silica that, when absorbed by plants, helps them to resist both fungal and insect attack. Because of its pure nature there is very little iron, alumina, soluble salts, carbonate or sand. There are minor concentrations of smectitic clays.
The deposit, made up of diatoms of the Melosira species was formed in a fresh water lake adjacent to a major Tertiary volcanic center. Our diatomite has the highest levels of amorphous silica of any commercial producer in Australia . Additionally, it is lowest in kaolin and sodium which gives it a most favourable pH and conductivity as well as soil solubility.
The Mt Sylvia Mine is located 38 kilometres south of Gatton in southeast Queensland . The diatomite horizon at Mt Sylvia has never been drilled and fully evaluated because it can be seen to outcrop on both sides of the spur and continuity can be inferred with a high degree of certainty. From this it can be assumed that there are reserves in excess of 600,000 tonnes .
This is sufficient to maintain a mining operation for a considerable time into the future at the maximum mining rate, given the current plant capacity, of 3,000 tonnes per annum.
Basalt: Overlying the diatomite are basalt flows, most of which flowed into, and reacted with the fresh water in the lake that contained the diatomite.
The alteration products produced by this event created the oxidised nature of the current basalt. The unique combination of clays and rock in the overburden renders it a most effective road base with a high compaction index. Mt Sylvia Diatomite is currently completing negotiations to secure an Extraction License to crush and screen the basalt and market it as DMR specification road base, road aggregate and source of basalt boulders.
The yellow-brown oxidized basalt fines that are stockpiled through the screening process are potentially a good soil conditioner-fertilizer. Geologically this material is called oxidized Palagonite. The quenched lavas that flowed into the lake formed abundant glass that subsequently devitrified to form a mixture of smectite clays and poorly crystallized feldspar. This material has a high cation exchange capacity (the ability to retain nutrients and water) and because it is derived from basalt, also contains a number of trace elements such as zinc, copper, cobalt, manganese and nickel that are important for both plant and animal health.