Rocksday

Diabase

Basalt's medium-grained cousin, formed in shallow sills and dikes.

Diabase specimen
Photo: CrankyScorpion at English Wikipedia, CC BY-SA 3.0, via Wikimedia Commons

How to identify diabase

  • Dark gray to black with small visible crystals.
  • Heavy and tough.
  • Lath-shaped feldspar between dark pyroxene.

Often confused with

Where it's found

  • Palisades, New Jersey
  • Preseli Hills, Wales
  • Karoo, South Africa

Uses

Crushed stone and 'black granite' monuments.

Rock tumbling

Great for tumbling.

Did you know?

Stonehenge's 'bluestones' include spotted dolerite brought from Wales' Preseli Hills.

Think you could spot it from a blurry close-up?

Play today's Rocksday