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A particulate hydrous mineral suitable for use as an opacifying pigment, filler or extender has a shape factor which is greater than S, where S is defined by Equation 1 as follows: S =( d 50 /0.036)+20  Equation 1;where d 50 is the mean particle size of the particles of the minera

A particulate hydrous mineral suitable for use as an opacifying pigment, filler or extender has a shape factor which is greater than S, where S is defined by Equation 1 as follows: S =( d 50 /0.036)+20  Equation 1;where d 50 is the mean particle size of the particles of the mineral measured in microns. The particulate mineral is preferably a kaolin, which is particularly suitable for use in aqueous matt paint compositions.

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1. A particulate hydrous mineral suitable for use as at least one of an opacifying pigment, filler and extender, which has a shape factor which is greater than S, where S is defined by Equation 1 as follows: S =( d 50 /0.036)+20  Equation 1;where d 50 is the mean particle size of

1. A particulate hydrous mineral suitable for use as at least one of an opacifying pigment, filler and extender, which has a shape factor which is greater than S, where S is defined by Equation 1 as follows: S =( d 50 /0.036)+20  Equation 1;where d 50 is the mean particle size of the particles of the mineral measured in microns, andwherein if the particulate hydrous mineral is kaolin, the shape factor of the particulate kaolin ranges from 70 to 140. 2. A particulate mineral according to claim 1, wherein the shape factor is greater than S, where S is defined by Equation 2 as follows: S =( d 50 /0.036)+25  Equation 2. 3. A particulate mineral according to claim 1 or 2, wherein the mineral is chosen from kaolin, ball clay, talc, mica, and vermiculite. 4. A particulate mineral according to clam 3 , wherein the mineral is kaolin. 5. A particulate mineral according to claim 4, wherein the mean particle size of the kaolin ranges from 0.4 μm to 3 μm. 6. A particulate mineral according to claim 5, wherein the mean particle size of the kaolin ranges from 0.5 μm to 2.0 μm. 7. A particulate hydrous mineral according to claim 4, wherein the kaolin has a shape factor ranging from 80 to 120. 8. A particulate hydrous kaolin suitable for use as at least one of an opacifying pigment, filler and extender which has a shape factor which is greater than S, where S is defined by Equation 1 as follows: S ( d 50 /0.036)+20  Equation 1;where d 50 is the mean particle size of the particles of the kaolin measured in microns, andwherein the kaolin has a linseed oil absorption of at least 50 grams per 100 grams of kaolin. 9. A pigment composition which comprises a blend of the mineral according to claim 3 together with one or more other white pigment materials. 10. A particulate hydrous kaolin according to claim 8, wherein the shape factor is greater than S, where S is defined by Equation 2 as follows: S =( d 50 /0.036)+25  Equation 2;where d 50 is the mean particle size of the particles of the kaolin measured in microns. 11. A particulate hydrous kaolin according to claim 8, wherein the mean particle size of the kaolin ranges from 0.4 μm to 3 μm. 12. A particulate hydrous kaolin according to claim 11, wherein the mean particle size of the kaolin ranges from 0.5 μm to 2.0 μm. 13. A particulate hydrous kaolin according to claim 8, wherein the shape factor of the kaolin is at least 40. 14. A particulate hydrous kaolin according to claim 13, wherein the shape factor of the kaolin is at least 60. 15. A particulate hydrous kaolin according to claim 14, wherein the shape factor of the kaolin ranges from 70 to 140. 16. A particulate hydrous kaolin according to claim 15, wherein the kaolin has a shape factor ranging from 80 to 120. 17. A particulate hydrous kaolin according to claim 8, wherein the kaolin has a linseed oil absorption of at least 60 grams per 100 grams of kaolin. 18. A pigment composition which comprises a blend of the particulate hydrous kaolin according to claim 8 together with at least one other white pigment material. 19. A paint composition comprisinga binder, anda pigment composition comprising a blend of a particulate hydrous mineral which has a shape factor greater than S,where S is defined by Equation 1 as follows: S =( d 50 /0.036)+20  Equation 1;where d 50 is the mean particle size of the particles of the mineral measured in microns, andat least one other white pigment material. 20. A paint composition according to claim 19, wherein the shape factor is greater than S, where S is defined by Equation 2 as follows: S =( d 50 /0.036)+25  Equation 2; 21. A paint composition according to claim 19, wherein the mineral is chosen from kaolin, ball clay, talc, mica, and vermiculite. 22. A paint composition according to claim 21, wherein the mineral is a kaolin. 23. A paint composition accor ding to claim 22, wherein the mean particle size of the kaolin is from 0.4 μm to 3 μm. 24. A paint composition according to claim 23, wherein the mean particle size of the kaolin is from 0.5 μm to 2.0 μm. 25. A paint composition according to claim 22, wherein the shape factor of the kaolin is at least 40. 26. A paint composition according to claim 25, wherein the shape factor of the kaolin is at least 60. 27. A paint composition according to claim 26, wherein the kaolin has a shape factor ranging from 70 to 140. 28. A paint composition according to claim 27, wherein the kaolin has a shape factor ranging from 80 to 120. 29. A paint composition according to claim 19, wherein the composition is a matt paint composition. 30. A paint composition according to claim 29, wherein the pigment composition further comprises titanium dioxide.