Like diamonds the lustre of a pearl is strong determinant of beauty and value. Lustre specifically refers to the glowing appearance of the pearl surface and its brilliance in reflecting light. A pearl of excellent lustre will be mirror-like whilst a pearl of poor lustre will look cloudy or milky.

Lustre is strongly influenced by the quality of the “nacre” secreted, the thickness of nacre coverage and the level of transparency it displays. The nature of the nacre is a direct consequence of the oyster’s health, its environment and the oyster’s species.

Pearl size is always expressed in terms of diameter and pearls are always measured in millimetres. Size does matter and every extra millimetre will inflate the value of a pearl by up to 200%.

Quite simply, the fewer the flaws, blemishes or spots evident on a pearl, the greater its value. A pearl’s skin quality will be graded on a commonly accepted scale. An “exceptional” skin is without blemish, “fine” is acceptable and a “marked” pearl is considered less valuable.

The colour of a pearl is a strong indicator of value in that a pearl of unique colour will typically be more precious but this must be considered in the context of other variables such as size, shape, lustre and the aesthetic appeal of the colour in question.

The colour palette for pearls is expansive with light colour pearls coming in shades of silver, white, pink, blue and gold. Darker pearls may be purple, charcoal, green or numerous shades of grey, approximating black.

The shape of a pearl has enormous bearing on its inherent value. As a rule a pearl that is round (ie. a symmetrical sphere) is considered the most precious but there is an assortment of shapes that are utilised to great effect and make for stunning jewellery pieces.

Round and oval (or off round) are the two prime shapes, followed by the semi baroque (tear drop, egg, pear or button shaped) and the baroque shapes, which includes asymmetrical and inconsistent forms. (Tadpole or mushroom)