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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.
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Obsidian is a natural volcanic glass, an extrusive igneous rock, it is produced when silica rich lava extruded from a volcano rapidly cools minimising crystal growth which gives the rock a fine, glassy texture. It is commonly found within the margins of rhyolitic lava flows known as obsidian flows, its high silica content (70 -75%) produces a highly viscous lava with some degree of polymerization. The inhibition of atomic diffusion through this highly viscous and polymerized lava explains the lack of crystal growth. It is hard and brittle rock with a black appearance due to the presence of conchoidal fractures, it therefore breaks with very sharp edges. It is this particular feature which has made obsidian an important rock in human history and evolution and why it is so well known and popular, as the sharp edges allowed it to be used in the past in cutting and piercing tools, most notably, arrow and spear heads. It has been used experimentally as scalpel blades in the past and recent years. These particular samples come from South East Mexico, the pieces will display typical black colouration and conchoidal fractures, making them suitable for both collectors, enthusiasts and educational use. Each sample will 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", Thin Section Slide |
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Obsidian, also known as ‘volcanic glass’ is a felsic, extrusive igneous rock. Crystal growth is minimal / absent within obsidian due to rapid solidification rates which inhibit crystal growth thus giving the rock a glassy appearance.
4 in stock
Obsidian is a naturally occurring volcanic glass derived from a rapidly cooled high silica lava. Often associated with the margins of Rhyolitic lava flows. It has little or no discernable crystalline structure. Specimens are supplied in a polythene bag in lots of 1 kg with a label.
This Mahogany obsidian is sourced in the United States of America. Impurities of magnesium and iron give this variety a red or brown appearance hence the name ‘mahogany obsidian’ or oak obsidian. Specimens are supplied in a polythene bag in lots of 1 kg with a label.
Out of 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
Phonolite igneous rock specimens, an intrusive crystalline version of nepheline syenite, this rock lies between felsic and mafic composition, collected from Traprain Law, Soctland, the name of the rock is derived from the ancient Greek word which means ‘sounding stone’. Which alludes to the feature this rock has of emitting a metallic ringing when struck. Samples are available in various sizes and come supplied in a card tray with a label.
53 in stock
Peridotite, found in Finland, is a dense, coarse grained igneous rock. It is commonly used in saunas due to certain porpertie. These rock specimens are ideal teaching aids or collectors specimens. Supplied in a card tray with label, offered in 3 optional sizes.
30 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
Diorite rock specimens from Cockermouth, Cumbria, is an intrusive igneous rock from the Ordovician period with a coarse, phaneratic texture composed of plagioclase feldspar, biotite mica as well as hornblende with intermediate chemistry. Found with the Skiddaw group, the rock samples are more suited for serious collectors and higher level education to describe the chemistry and mineralogy of various igneous groups. Available in 3 sizes and supplied in a card tray with an information label.
36 in stock
Grey granite rock specimens from Scotland, featuring the main mineral components expected in granite such as quartz, feldspar and mica. The quartz is slightly smokey, giving the specimens an overall grey appearance. Available in 3 optional size.
Out of stock
An igneous rock exhibiting a porphyritic texture containing large cubic crystals of feldspar within a fine grained matrix. Collected near Oslo, Norway. Each sample is supplied in a labelled card tray. Each sample is supplied in a labelled card tray.
56 in stock
Dunite igneous rock specimens from the Gusdal olivine pit in Åheim, southern Norway. Composed of green olivine minerals with chromite and pyroxene crystals, the rock forms as intrusive igneous plutons in the earth mantle down to 400 km deep and displays a coarse texture and green colouration. Overall, the samples are fairly granular and weak due to their chemistry and form part of the basal gneiss complex of southern Norway. Ideal for various levels of collectors and for higher level education and research use, the samples are available in three sizes and come supplied in a card tray with an information label.
25 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
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
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
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
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