Mineral necessarily constant for all sides, which is a function of its structure; crystallographic weakness renders some directions softer than others. An example of this property exists in kyanite, which has a Mohs hardness of 5½ parallel to [001] but 7 parallel to [100]. The most common scale of measurement is the ordinal Mohs hardness scale. Defined by ten indicators, a mineral with a higher index scratches those below it. The scale ranges from talc, a phyllosilicate, to diamond, a carbon polymorph that is the hardest natural material. The scale is provided below: Lustre indicates how light reflects from the mineral's
Emerald Lingam Emerald Lingam Emerald Lingams are established in many Hindu Temples in Tamil nadu. Emerald (Tamil: மரகதம்)is a variety of the mineral beryl (BeAl(SiO)) colored green by trace amounts of chromium and sometimes vanadium. The hardness of Beryl is 7.5–8 on the 10 point Mohs scale of mineral hardness. The toughness (resistance to breakage)of Emerald is classified as generally poor, hence most emeralds are highly included. Emerald is a green gemstone. Emerald means the shade of green color. Because of its green color, the term Emerald is employed. Emerald is also associated with the eighth planet Mercury in the Solar System.