尽管受到尊敬，但古人很快就认识到黄金的实用性，尤其是它的延展性，这使它成为制作珠宝的理想材料。

Despite their reverence, the ancients were quick to recognize gold's practical qualities, particularly its malleability, which made it ideal for jewelry.

youdao

而一旦把延展性引入进来，材料就变得脆弱了。

Once ductility is introduced, materials become weak.

youdao

当晶体大小大约为3纳米（1纳米等于10亿分之一米）时，天然丝材料具有超强的强度与延展性特征。

When the crystal size is about three nanometers (billionths of a meter), the material has its ultra-strong and ductile characteristics.

youdao

So you don't have ductility, which is what you have in metal.

所以材料不具备延展性，而且金属中有自由电子。

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