Aries Venus being the lord of 2nd and 7th houses is extremely fatal .It is also not the friend of mars .Still then diamond can be worn in major period of venus if venus is in its own sign or exalted.
Taurus Venus is the lord of ascendant in taurus .This is a jeevan ratna. It should always be worn.
Gemini Venus is the lord of 5th and houses in this sign . The Mool trokona sign of venus falls in 5th trine. So it is considered to be auspicious. There is friendship between venus & mercury. Diamond worn in the major period of venus proves to be very favorable.
Cancer Venus is the lord of 4th and 11th houses . There is no friendship between venus and moon .
Leo Venus is not benefic since it is the lord of 3rd and 10th house. Venus and sun the lord of ascendant are not friends. Diamond should be worn only in the major periods of venus .
Virgo Venus is the lord of 2nd & 9th house. Being the lord of trine it is very much benefic .
Libra Diamond is the jeevan ratna of venus in libra . Venus is the lord of ascendant and eight houses. It is not malefic since it is lord of ascendant also.
Scorpio Venus being the lord of 12th and 7th houses is not considered to be benefic in scorpio. Apart from this there is no friendshipbetween mars and venus .
Sagittarius Venus is not benefic in Sagittarius as it is the lord of 6th and 11th houses.Venus is the enemy of Jupiter the lord of ascendant . diamond might prove to be favorable in the major period of venus if it posited in 1st , 2nd , 4th , 5th , 9th or 11th house .
Capricorn It is favourable and yogakaraka for the natives of this sign . Venus is the lord of 5th and 10th houses . Venus and saturn the lord of ascendant are friends . Diamond must be worn in the main period of venus .
Aquarius it is very much favorable .In this sign venus being the lord of 4th and 9th houses is also the friend of saturn .
Pisces Venus is malefic as it is the lord of 3rd and 7th houses . Besides it is also enemy of jupiter .