DIY Temperature Control using a PID control and a solid state relay. Category. License.
The difference between regular shungite and elite or noble shungite is in the proportion of organic carbon in it. Regular shungite contains from 35 to 60 per cent of organic carbon while the percentage of carbon in elite shungite is much higher and totals from 92 to 98 per cent.
Nephrite and jadeite. Nephrite and jadeite were used from prehistoric periods for hardstone carving. Jadeite has about the same hardness as quartz. Nephrite is slightly softer but tougher (more resistant to breakage) than jadeite. It was not until the 19th century that a French mineralogist, Alexis Damour (1808-1902), determined that jade was in fact two different minerals.