the hard alloys according to the present invention are achieved by the formation of ordered regions within the metal alloy , ‘ ordered regions ’ meaning the existence of a super - lattice structure , in which the location of different atomic species is periodic and predictable , rather than simply being a random solid solution of different atomic types . the preferred type of ordered region has the stoichiometry x 8 y , where x is the parent metal and y is the solute atom type . a preferred alloy is a platinum alloy and pt 8 x is believed to exist in the following alloys set out below . other preferred alloys include palladium and nickel alloys and the same stoichiometry also exists in these alloys . this has been predicted from first thermodynamic principles known in the art [ a . j . ardell , metallic alloys : experimental and theoretical perspectives , 93102 ( 1994 ). z . w . lu and b . m . klein , phys . rev . b 50 , 5962 - 5970 ( 1994 )]. ptti : the pt 8 ti structure has been predicted , observed , and reported in the open literature . p . pietrowski , nature , 206 , 291 ( 1965 ). ptv : the pt 8 v structure has been predicted , observed and reported in the open literature d . schryvers , j . van landuyt and s . amelinckx , mat . res . bull , 18 , 1369 ( 1983 ). ptzr : the pt 8 zr structure has been predicted , observed and reported in the open literature . p . krautwasser , s . bhan and k . schubert , z . metallkd . 59 , 724 ( 1968 ) ptcr : the ptbcr structure has been predicted and was observed by the applicant . ptnb : the p % nb structure has been predicted , but not yet observed . ptmo : the pt 8 mo structure has been predicted , but not yet observed . pthf , ptta , ptw : the pt 8 hf , pt 8 ta and pt 8 w structures have been predicted , but not yet observed . ( it will be appreciated that these latter systems are less urgent because the pt 8 x occurs at above 10 wt . % solute and such an alloy therefore does not meet south african hallmarking requirements .) without wishing to be bound by theory , it is believed that the reason that the x b y structures have been observed so rarely in the art is because the kinetics of the ordering transformation are very slow . the applicants have found that the kinetics can be accelerated by appropriate cold work . it must be appreciated that the acceleration of the kinetics is not essential according to the present invention . if the kinetics for a particular alloy are slow , the kinetics can be accelerated by quenching from high temperatures and / or the kinetics can be accelerated by irradiating the metal alloy . the applicants have found that the formation of the pt 8 x structure confers an impressive increase in hardness to an alloy — something that has not previously been observed . for example , when the ptv structure forms in the 3 . 2 % . wt ptv alloy , a hv of over 500 is achieved . this is a significant value compared to the hv of cold - worked stainless steel at 400 . the above hv of over 500 is particularly surprising considering the hv of the annealed 3 . 2 % . wt ptv alloy is approximately 210 and the hv of the cold worked alloy is approximately 360 . ( annealing is heat treatment designed to negate the effect of cold working .) to achieve this elevated hardness ( higher than any other platinum jewelry alloy ), the alloys according to the present invention must be heat treated to produce the pt 8 x structure . there are several important practical considerations here : the method comprises only a single heat treatment , of as short a duration as 15 minutes . no further change in hardness is observed following heat treatments of up to 2500 hours . by comparison , precipitation hardening , which produces the next highest hardening in jewelry alloys , requires two heat treatments , possibly lengthy . the heat treatment temperatures ( which differ from alloy to alloy ) are between 300 - 1000 deg c .,— the slow kinetics of the pt 8 x transformation are greatly accelerated by cold work prior to heat treatment . since most jewelry processes involve cold work anyway , this would not have to be an additional step . in other words , once a jewelry item has been made by ( cold ) hand - working of an alloy , it can simply be placed into a furnace for approximately 15 minutes at a temperature below the t rx for that alloy to induce the formation of x 8 y stoichiometry . this will confer a greater hv to the alloy than heretoknown before and may even confer the alloy with a hv higher than stainless steel . further features of a method of hardening low - solute platinum alloys , in accordance with the invention , are described hereinafter by way of the following non - limiting examples and figures . fig1 is a graph of hardness vs . heat treatment temperature for platinum 3 . 2 wt . % vanadium alloy heat treated for three hours . fig2 is a graph of hardness vs . time for platinum 3 . 2 wt . % vanadium alloy heat treated at 400 deg c . fig3 is a graph of hardness vs . heat treatment temperature for platinum 2 . 9 wt . % chromium alloy heat treated for three hours . fig4 is a graph of hardness vs . time for platinum 2 . 9 wt . % chromium heat treated at 300 deg c . fig5 is a graph of hardness vs . heat treatment temperature for platinum 5 . 2 wt . % molybdenum heat treated for three hours . in fig1 , 3 and 5 , the hardness of the cold worked alloy is shown at heat temperature treatment 0 . with reference to fig1 and 2 , a method of manufacturing an item of jewelry from a platinum alloy containing 3 . 2 wt . % vanadium in accordance with the invention is described hereinafter . the platinum alloy is cast and homogenised to provide an alloy having a uniform structure . the term ‘ uniform structure ’ refers to compositional homogeneity and an equiaxed grain structure . the platinum alloy is then cold worked to produce the jewelry item by a process of rolling , drawing or any other suitable means of working , resulting in a hv of approximately hv 100g 366 . the jewelry item is then heat treated in a furnace at a temperature below 600 ° c . for three hours , followed by cooling to room temperature . after the heat treatment the jewelry item has an enhanced hv of approximately 500 which is higher than the hv that can be attained by cold working , i . e . approximately 360 . with reference to fig3 and 4 the platinum / chromium alloy is cast and homogenised to provide an alloy having a uniform structure . the platinum alloy is then cold worked to produce the jewelry item by a process of rolling , drawing or any other suitable means of working , resulting in a hv of approximately hv 100g 295 . the jewelry item is then heat treated in a furnace at a temperature below 600 ° c . for three hours , followed by cooling to room temperature . after the heat treatment the jewelry item has an enhanced hv of approximately 330 which is higher than the hv that can be attained by cold working , i . e . approximately 295 . with reference to fig5 the platinum / molybdenum alloy is cast and homogenised to provide an alloy having a uniform structure . the platinum alloy is then cold worked to produce the jewelry item by a process of rolling , drawing or any other suitable means of working , resulting in a hv of approximately hv 100g 360 . the jewelry item is then heat treated in a furnace at a temperature below 600 ° c . for three hours , followed by cooling to room temperature . after the heat treatment the jewelry item has an enhanced hv of over 400 which is higher than the hv that can be attained by cold working , i . e . approximately 360 .