Basalt is a fine-grained, hard, dense rock. The most common rock on the Earth, Moon and Mars and it has erupted from volcanoes scattered throughout New Zealand. Igneous: Rock formed from lava flows (therefore technically a 'volcanic igneous' rock). Source location: Canterbury. Sizes: Choose from dropdown menu: Small specimen, Hand specimen, Shelf specimen or Extra large shelf specimen. Note: Images are examples of specimens only. Sizes and shapes will vary. More detail Structure Basalt is a fine-grained igneous rock with a dense and homogeneous structure. It is typically composed of minerals such as pyroxene, plagioclase feldspar, and olivine. Type Volcanic igneous. Physical Properties of basalt Colour: Typically dark grey or black in colour. Lustre: Dull to glassy lustre, depending on its texture and mineral composition. Hardness: A relatively hard rock, ranging from 5 to 6 on the Mohs scale. Density: Ranges from 2.8 to 3.0 grams per cubic centimetre. Fracture: Exhibits a conchoidal fracture, meaning it breaks with smooth, curved surfaces resembling the interior of a seashell. General Properties of basalt Fine-Grained Texture: Has a fine-grained texture due to its rapid cooling from lava or magma, resulting in small mineral crystals. Interlocking Structure: Its minerals form an interlocking structure, contributing to its strength and durability. Weather Resistance: Highly resistant to weathering, erosion, and chemical attack, making it suitable for outdoor applications. Heat Resistance: Has excellent heat resistance and can withstand high temperatures without significant deformation or damage. Low Porosity: Relatively low in porosity, making it less susceptible to water absorption and freeze-thaw damage. Uses of basalt in New Zealand and worldwide Early Māori: Basalt (karā) was used to make stone clubs (patu ōnewa). Construction: Widely used as a construction material, including for building facades, walls, and road construction. Paving: Its durability and resistance to weathering make it suitable for paving stones, footpaths, and driveways. Landscaping: Used in landscaping projects for retaining walls, decorative features, and pathways due to its natural beauty and durability. Aggregate: Crushed basalt is used as aggregate in concrete, asphalt, and road construction. Railway Ballast: Utilised as railway ballast, providing stability and drainage to railway tracks. Dimension Stone: Can be cut and polished into slabs for architectural purposes, including countertops, tiles, and monuments. Geological Studies: Studied by geologists to understand volcanic processes, lava flows, and the history of Earth's crust.
