Is it possible for a black-hole to easily stretch or turn any hard object like (Diamond , Gold bar , Platinum bar , Brass) into spaghettification state in just a seconds or minute once it gets near nor reached the black-hole's event horizon??

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It depends on the size of the black hole and the size of the bit of material you are trying to pull apart, as well as what it is made of. What is important is the difference in gravitational pull between one end of your sample and the other. This difference force grows as the inverse of distance cubed as one moves in towards the black hole.

However, nothing special marks crossing event horizon and if we were talking about a supermassive black hole (a million solar masses or more), you might not even notice it had happened, since the force difference, sometimes called the tidal force, would be quite small. At the event horizon of a smaller black hole, the tidal force would be much larger. To see this, we note that the difference in force between two ends of a bar of length $\Delta r$ is approximately $$ F = \frac{8GM}{r^3}\Delta r,$$ where $M$ is the black hole mass. At the event horizon $r = 2GM/c^2$, so $$ F = \frac{c^6}{G^2M^2}\Delta r.$$

The spaghettification force continues to increase as the object heads towards $r=0$, which will occur in a finite proper time for the falling object. So it will always increase sufficiently to rip something apart, no matter what it is made of; the question is merely at what radius does this happen.

It is of interest however to calculate whether it would happen to an object outside the event horizon, simply because then an external observer (at a safe distance) might witness it. This in turn depends on the material making up the object, it's size and the mass of the black hole.

Consider a material of tensile strength $T$, size $\Delta r$ and cross-sectional area $\sim (\Delta r)^2$. For this to break up before reaching the event horizon then the tidal force at the event horizon must exceed $T (\Delta r)^2$ and thus $$ \frac{c^6}{G^2M^2}\Delta r > T (\Delta r)^2 $$ $$ M < 2\times10^5 \left({T \Delta r}\right)^{-1/2}\ M_{\odot}$$

Diamond has $T\sim 10^{11}$ N/m$^2$. If it was of size 1 cm, then a black hole would need to be larger than 6 solar masses for this chunk of diamond to survive being ripped apart outside the event horizon. Other materials or larger bits of material are easier to break and would not survive outside the horizon of even more massive black holes. e.g. The tensile strength of bone is about $10^{8}$ N/m$^2$, so a 0.1m piece of bone would be pulled apart prior to falling through the event horizon if $M< 60M_{\odot}$.

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