This post is only a suggestion based on other sources, members can have their own opinions and practice.
Why women should not wear Gold Ornaments below their waist:
Atharva Veda says that gold comes from Agni Deva. Sun God is in Gold. Moon-god is in Gold with lustre. May be with this reason the gold ornament is used only above waist.
There is only one exception. The leg ornaments of temple deities are gold.
Even great kings and very rich in Bharath did not have golden chappals.
On wearing gold some information are shared as below.
1) Advantages of wearing Gold:
Atharva veda, Kandam (Book) 19, Suktam 26, Verse 1;
"अग्ने: प्रजातं परि यत् हिरण्यम्
अमृतं दघ्रे अधि मर्त्येषु ।
य एनव्देद स इदेनमर्हति
जरामृत्युर्भवति यो बिभर्ति ।।"
This means that, I adorn gold created or orginated from fire which bestows eternity. One who adorns it is liberated from the fear of untimely death.
Atharva veda, Kandam (Book) 19, Suktam 26 (all the Four Verses) Translation from Ralph T.H. Griffith, [1895]
1 Gold that was born from Fire is immortal hath been deposited
with mortal creatures.
He who knows this deserves to own this jewel, and in extreme
old age dies he who wears it.
2 The men of ancient time with children round them longed for
this Gold, bright with the Sun's own colour,
This shall endow thee, as it shines, with splendour, and long
shall be the life of him who wears it.
3 Long life and splendour let it bring energy and strength to thee.
That thou mayst shine among the folk with all the brightness of
the Gold.
4 What Varuna the King knows well, and what the God
Brihaspati,
And Indra, Slayer of the Foe, may that bestow long life on thee,
may that increase thy splendid strength.
2) Adorning gold ornaments in the upper part of the body:
In the ancient tradition of adorning ornaments, an important point is that gold ornaments are adorned above the waist. The spiritual reason for this is that gold ornaments have predominance of the Absolute Fire Principle. Through this one is protected from the negative energies active in the direction 8 to 10 feet upwards from the ground. Also, due to gold the negative energies have distress.
3) Spiritual science underlying adorning silver ornaments below the waist:
Silver has more ability to absorb the raja predominant, Chaitanya laden desire frequencies. By adorning silver ornaments below the waist, the woman is protected from the distressing Absolute Earth and Water Element frequencies emitted from Hell. In this way by adorning silver anklets, the negative energies cannot enter a woman’s body easily. Similarly she is protected by all the ornaments like griddle, toe rings etc.
Please also read from the link below to know the Significance of Women/men wearing different types of ornaments in different parts of the body.
http://indyas.hpage.co.in/unknow-facts-about-hindu-religion_9526511.html
Why are gold ornaments worn in the upper part of the body? | Achardharma (Practicing Dharma)
Atharva Veda: Book 19: Hymn 26: A hymn accompanying investiture with an amulet of gold