Lamprophyre
“The dark dyke intruder”
Igneous
Lamprophyre is a group of dark, porphyritic igneous rocks that typically occur as dykes and sills. They're characterized by abundant dark mica and amphibole crystals set in a fine-grained matrix, and they often form in association with major tectonic and magmatic events.
Composition
biotite, phlogopite, hornblende, augite, olivine, feldspar
Where Found
Scottish Highlands, Black Hills (South Dakota, USA), Quebec (Canada), Ballarat (Australia)
Mohs Hardness
5-6
Fun Fact
Gold miners learned to pay close attention to lamprophyre dykes because gold deposits are frequently found at or near the contact zones where these rocks intrude.
Test Your Knowledge
Why are lamprophyre dykes frequently associated with nearby gold mineralisation?
Related Specimens
Want to identify rocks yourself?