Select two Z columns (XYZZ) or a range of data from two Z columns. The Z columns may be multiples of 2, in which case, Z-Z pairs will be grouped in the layer and plot Symbol Edge Color will be incremented.
Highlight the source data and
select Plot > 3D: 3D Tetrahedral.
(Installed to the Origin program folder).
Unlike 3D graphs in the Cartesian coordinate system, there are four axes in the 3D ternary system, defined as X, Y, Z and Zh. The Zh axis is perpendicular to the plane of the triangle. Correspondingly, there will also be four axis planes: XY, YZh, ZhX and ZZh (see the Planes tab in Plot Details).