Dolomite - sedimentrary rock made of the mineral dolomite (Ca,MgCO3), similar to limestone Dolerite (Diabase in USA) - intrusive igneous rock Diatomite - sedimentrary rock rich in he emains of diatoms
If a ring made of ferromagnetic substance is kept in the magnetic field, the lines of force will rush through the magnetic material leaving the central gap free from lines of force. The thing kept in the central space will not be affected by the lines of force.
I would think that you would shield a magnetic field the same way you would shield a sensitive sensor from that same kind of field, encase it with a fine metallic mesh covering and ground the covering.
Igneous rock : Dolerite, Dacite, Diorite, Ditroite, Dunite, etc Sedimentary rock : Dolomite, dismicrite, diamictite Metamorphic rock : Diabase It may even be possible that you are searching for the term Dyke, which is not a rock name but the name of a particular mode of emplacement of intrusive igneous rocks.
Dolomite _ magnesian carbonate rock Dolerite - basic igneous hypabyssal (near surface intrusive) rock Diabase - another name for dolerite Diamictite - an unsorted conglomeratic sedimentary rock Diorite - an intermediate plutonic igneous rock
