DIAMOND

Diamond is the hardest mineral on earth,and combined with its exceptional luster and brilliance, is the most prized of all gems. Pure and colourless diamond is the most popular but other varieties like yellow,brown,green,pink,blue and red ,even black are also found. Diamond is chemically Carbon and the formula is C. Because of the uniform arrangement of the carbon atoms, diamond crystals are well formed. Diamond forms at very high temperatures and pressures like 80 KM under ground. These days Australia is main producer. Ghana,Sierra Leone,Zaire,Botswana,Namibia,USA,former USSR and Brazil also produce Diamonds. Diamonds are graded for four "C"s for gem quality—Colour; Clarity; Cut; Carat i.e. weight.
Diamond has hardness of 10.specific gravity 3.52,Refractive index 2.42 with a Cubic crystal structure.
Diamond is the precious stone for Venus. The semi precious substitute for this is Tourmaline and Rock Crystal.
Tourmaline is basically complex Borosilicate gemmologically. The formula for this is Na(Li,Al)3Al6(Bo3)Si6O18(OH)4.It comes in various colours and has different names as well, but the colourless tourmaline is called Anchorite and is used for Venus. This variety occurs in pegmatites of Madagascar and Pala(in California in USA).
The hardness of Anchorite is 7.5,specific gravity 3.06,refractive index 1.62-1.64 with Trigonal structure.
Tourmaline helps in sleep disorders and is widely used for this. The stone decreases fear, worry and stress and helps increase sleep. It also acts as a balance force for eyes, brain, thymus and thyroid.
Rock crystal is Quartz and is the most common mineral of the earth. It is Silicon Dioxide with a formula SiO2. The crystals are usually found as hexagonal prisms with pyramidal ends. It is found worldwide but the most important sources are Brazil, Swiss and French Alps,Madagascar,USA,former USSR.
The hardness of this stone is 7,specific gravity 2.65,refractive index 1.54-1.55 with a Trigonal crystal structure.
Quartz helps increase lactation, tissue regeneration, eyesight, and detoxification. It helps decrease anaemia, jaundice, asthma, constipation, headache, fever, pain, ulcers ,leukemia, bubonic plague, radiation protection, sore throat, gland swellings, vertigo ,dizziness, burns and blisters. It balances cell salts, circulation, amino acids, protein, stomach lining, immune system, pituitary gland and intestines.