Freshwater : generally nucleus free, mainly from China , many shapes, colours & sizes from 2 to 16mm or even larger. Many natural shades plus dyed colours available.

Marine : usually with a bead of shell nucleus, often from Japan, best and original type is 'Akoya' with sizes 2 to 10mm in pale colours - cream, white, pink and silver.

Keshi : irregular shaped 'blobs' of pearl that resemble hot metal dropped in water, up to 20mm across colours depend on the oyser of mussel variety.

Tahitian : from French Polynesia and the Cook islands, naturally dark colours including black/green, aubergines, violet, browns and gold. Large sizes 8 to 18mm

South Sea : valuable natural  pearls from Australia, Indonesia and the Phillipines,
large sizes 10 to 22mm, range in colour from silvery white and cream to champagne and gold.

Lustre : this refers to the sheen of the pearls. A good pearl should be deeply lustrous - the deeper the coating of nacre the better the lustre will be.

Texture : the best pearls are ideally flawless, without any blemishes or dents.

Shapes : they can be many different shapes but the most common are round, button, drop, oval and baroque ( meaning irregular). Fancy shapes are also achieved by put a carved or special shape mother of pearl bead into the oyster or mussel to be coated with nacre.  Perfect examples of each shape are the most highly prized.

Size : pearls are sized in millimetres and depends on the size of the original nucleus and the thickness of the nacre, which is deeper the longer the pearl has been given to develop.

Colour : mostly down to personal choice and fashion, good strong deep and even colours are most valuable.