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Olivine dolerite igneous rock specimens from Clee Hill, Shropshire, UK, composed of pyroxene minerals such as augite and magnetite as well as plagioclase feldspar. The samples are fine grained and crystalline in texture with a dense weight and black colouration. Similar in appearance to gabbro and basalt, the rock samples are suitable for serious collectors or higher level education to explain the difference in chemistry and mineralogy of igneous rocks. The samples are available in three sizes and supplied in a card tray with an information label.
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Olivine dolerite, a variant of dolerite, also known as diabase, is an intrusive fine grained igneous mafic rock with a crystalline texture. It is sub-volcanic in origin, forming at medium to shallow depths within the earths crust, usually less than 2 Km deep and similar in composition to gabbros and basalts, sometimes being confused as such upon first inspection. The rock is black in colour and is composed of expected mafic minerals such as augite and magnetite as well as plagioclase feldspar laths. As expected from the name, olivine is also present in quantity in these samples which can be viewed under hand magnification as dark green crystals within the rock but can be visible with the naked eye as some are up to 3 mm in size. These samples come from Clee Hill, Shropshire, UK in an area rich in carboniferous coal seams which have been intruded by numerous olivine dolerite sills which are suspected to have formed during the Westphalian stage of the Permian period, 295 million years ago. Due to the hardness of the dolerite, the surrounding rocks were more susceptible to erosion, resulting in the igneous rock being visible the most, with its black colouration, the stone is known locally as ‘Dhustone’, derived from the Welsh word for ‘Black stone’. Samples are fairly dense due to the abundance of iron bearing pyroxene minerals, overall, they are suitable for collectors, particularly those interested in igneous activity as well as higher level education to indicate various igneous rocks and chemistries one may come across in the field, especially among rocks which may look like another upon first glance. Specimens are available in various sizes and come supplied in a card tray with an information label.
Weight | 130 g |
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Specimen Size | 2" x 2", 3" x 2", 4" x 3" |
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Amygdaloidal basalt is an igneous rock which is extrusive in nature, these specimens formed over 60 million years ago during the Tertiary period and come from Ireland. They are part of the Antrim lava group and exhibit a dark colouration with occurrences of amygdales containing quartz and calcite crystals. As a basalt they are somewhat dense, but lighter than pure samples due to the cavities within them which formed as a result of gaseous activity during their ejection. Over time, hydrothermal fluids pass through the rock and minerals form within the cavities, which gives the usually dark coloured rock a speckled appearance. These samples are available in various sizes and are suitable for higher educational use to detail the subtle differences between similar igneous rocks, they come supplied in a card tray with an information label.
69 in stock
These specimens of ‘Preseli Bluestone’ are a form of Spotted Dolerite. The samples originate from the Preseli Hills of Wales, and were transported by a glacier & deposited as glacial erratics. Specimens are supplied in a polythene bag in lots of 1 kg with a label.
Out of stock
Ignimbirte welded tuff is a pyroclastic rock of any origin formed through volcanic processes, the rock appears to show streaks of welded material on some surfaces and appears to be rhyolitic on the inside. Specimens come from Cumbria and are available in various sizes.
78 in stock
Pink granite rock specimens from China, containing the expected granite minerals, however, these specimens are higher in biotite mica, thus making the pieces seem darker than other pink granites.
88 in stock
Hand size specimens of the big feldspar variant of gabbro, samples were collected from Carrock fell, Cumbria, UK and can be supplied in 3 sizes.
71 in stock
Essexite igneous rock specimens from Lanarkshire, Scotland, UK, also known as olivine or nepheline monzogabbro is an intrusive rock with mafic chemistry, composed of nepheline and plagioclase feldspar along with olivine, magnetite minerals as well as augite phenocrysts which exhibit euhedral crystal forms. The rock has a dense weight and overall dark colouration but attractive appearance. It is locally known as Crawfordjohns and was highly sought after as a high quality material to produce curling stones. These samples are excellent for young and older collectors as well as higher educational use, the pieces are available in three sizes and come supplied in a card tray with an information label.
61 in stock
Obsidian is an extrusive igneous rock, these specimens exhibit a typical black colouration with conchoidal fractures, they come from South East Mexico and are excellent for educational use and collectors due to the quality. This igneous rock forms when magma extrudes onto the earths surface, chemically it is silica rich and impurities give the black colouration. It’s fine crystalline texture and fracture makes obsidian appear glassy and it breaks as such. The pieces are available in various sizes and come supplied in a card tray with an information label.
Volcanic scoria rock specimens from Italy with a deep red colouration and numerous vesicle displaying text book quality. Formed when basaltic or andesitic magma or lava reaches the earth surface, the escaping gases leave behind pockets which remain even after the lava has solidified. Samples are available in optional sizes and come in a card tray with a label.
61 in stock
Rhyolite specimens found in Cumbria. Rhyolite is a felsic (silica rich) rock, often formed in highly explosive volcanoes. Specimens are supplied in a card tray with label.
61 in stock
Accretionary lapilli tuff is an igneous pyroclastic rock, these samples come from Longsleddle, Cumbria in the UK and forms when hot ash and debris is ejected from as volcano. Some of this material is held together by moisture and once heavy enough, falls into the ash below forming small ‘spots’ within the material, creating a speckled rock. The samples are suitable both for young and serious collectors as well as educational use and are supplied in various sizes with a card tray and label.
67 in stock
Pink Granite, rich in potassium feldspars giving the distinctive pink hue, easily identifiable as a granite due to its mineral composition. Specimens come from Scotland and are supplied in a card tray with label.
8 in stock
Larvikite is an igneous plutonic rock and variant of monzonite from Larvik, Norway, due to its chemistry, it is composed mainly of orthoclase, albite and anorthite along with plagioclase which gives the rock a blue to silver shimmering effect. The igneous pluton formed during the Permian period, 292 – 298 million years ago during the the Variscan orogeny. A beautiful rock to observe due to its coarse crystalline texture and schiller effect, the samples are ideal for general interest, collectors and educational use with specimens being available in three sizes and come supplied in a card tray with an information label.
140 in stock
Snowflake Obsidian found In Anatolia, Turkey is characterised by pale radially clustered crystals of Cristobalite set in an otherwise black vitreous matrix. Each sample is supplied in a labelled card tray.
Out of stock
Bytownite basalt is another variation of the common Basalt rock. These particular samples come from Cumbria and are available in a range of sizes.
196 in stock
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