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Bituminous coal is a high-grade coal found in New Zealand. The shiny, black rock is highly valued worldwide for steel production and heavy industry, but it is also considered a significant polluter and contributor to greenhouse gas production. It does not contain recognisable plant fragments.
THIS PRODUCT SHOULD NOT BE USED FOR HEATING OR COMBUSTION EXPERIMENTS INDOORS. It burns exceptionally hot, produces sticky black soot, and is very hard to extinguish.
Sedimentary: Formed from the accumulation and burial of dead land-based plant material (therefore technically an 'organic sedimentary' rock).
Source location: West Coast, South Island (primarily the Buller and Greymouth coalfields).
Sizes: Choose from the dropdown menu: Small specimen, Hand specimen, Shelf specimen or Extra large shelf specimen.
Images are examples of specimens only. Sizes and shapes may vary.
Storage: Unlike lower-grade coals, bituminous coal does not suffer from 'slacking' (crumbling due to moisture loss) and is highly stable. Store it in a standard specimen tray or container, keeping it out of direct sunlight to protect its natural glassy lustre.
More detail
Structure
Bituminous coal is a sedimentary rock composed mainly of carbon-rich plant material such as wood, bark, roots, leaves, etc. (essentially peat). The burial and compaction of this organic matter occurs over millions of years under intense geological heat and pressure. Because of the layered nature of the original organic deposits, the coal itself demonstrates a distinct layered or banded structure of alternating shiny and dull rows.
Type
Organic sedimentary rock.
Physical properties
Colour: Typically pitch black or dark brownish black.
Lustre: Shiny, glassy, or almost metallic.
Hardness: Brittle and blocky. Relatively soft, with a hardness ranging from 1 to 3 on the Mohs scale.
Density: Ranges from 1.1 to 1.5 grams per cubic centimetre. Denser than sub-bituminous coal and lignite.
General properties of anthracite and semi-anthracite
Carbon content: Has a high total elemental carbon content, usually ranging from 80% to 88% on a dry basis in NZ specimens (with a high raw fixed carbon content ranging from 40% to 90%).
Combustibility: Highly combustible and releases an exceptional amount of intense heat when burned.
Formation: Forms from the deep compression and heating of sub-bituminous coal. Note for NZ students: While most global coal is over 300 million years old, NZ bituminous coal is unique because it is geologically "young"—formed only 30 to 70 million years ago from evolved flowering plants.
Energy content: Has a very high energy content, making it a premium and valuable fuel source for specialised industrial processes.
Uses in New Zealand and worldwide
Fuel: NZ's bituminous coal is too valuable to burn for general electricity. It is almost entirely exported to international markets (primarily in Asia) for industrial use.
Steel production: Highly sought after as coking coal. It is baked in oxygen-free ovens to create "coke" (a pure carbon fuel), which acts as a crucial reducing agent in traditional blast-furnace steel manufacturing globally.
Industrial processes: Utilised worldwide in heavy industrial processes, including cement manufacturing, specialised paper production, and chemical processing.
Residential Heating: Historically used for home heating in NZ due to its high heat output, but this has been entirely phased out and restricted by regional clean air regulations due to its heavy, sticky smoke.
Carbonisation: Readily subjected to carbonisation to produce valuable coal tar and by-products, which are used to manufacture synthetic materials, chemicals, and plastics.