Here's a shot of some magnesite beads showing the enhanced matrix that we think is produced with heat/cold and brown dye.

This brown/black matrix is often crisper looking than the black matrix lines worked into the "block" plastic material. You have to look very closely to see the difference between spider web matrix in real turquoise, the enhanced matrix in magnesite and the markings swirled into the platic "block" material.

One of the best sites on the web to see high quality real turquoise is Skystone trading in Sante Fe. They show the "good stuff."