If the rock is granite, as you say, there's no way the metal pins
could have survived the temperature and pressure. Read up on what it
takes to create an igneous rock.

It was embedded into the rock at some time after the rock's creation. 

On 16 Feb 2004 16:23:22 -0800, wizguru@tsc-global.com (John J.
Williams) wrote:

} Several years ago, I found a granite rock with an embedded modern
} manmade-like connector-like component. My rock is featured in the Feb.
} 2004 issue of UFO Magazine, and also I've been told in an upcoming
} Spring edition of Fortean Times (in Letters section). Don't miss
} either article. This media exposure has provided quite a bit of
} excitement.
} 
} However, without further evaluation, I do not yet know with certainty
} whether my rock is of UFO or lost advanced civilization origin, or
} whether the embedded component is modern manmade and for some
} unexplained fluke or reason ended up embedded in my rock. If my rock
} is indeed a genuine artifact of UFO or advanced civilization origin,
} then it should be able to tell us much about their technology; and my
} rock may also be the hard evidence that skeptics have been screaming
} about for decades that proves the existence of UFOs or lost advanced
} civilizations.
} 
} The webpage below shows clear photos of my rock, plus much descriptive
} material about it. Please visit it:
} 
} www.tsc-global.com/rock.htm
} 
} I am looking for the following contributions:
}     (1) Professional independent evaluations of my rock. There is some
} urgency in doing this because unless and until my rock is determined
} to be a genuine artifact, I will not go through the substantial time
} and expense to take particular actions to obtain and preserve the site
} where I found it, which risks degradation due to human exposure. All
} the help I can get from everyone to speed this process along might
} make a real difference.
}     (2) For those who believe that my rock's component is modern
} manmade, I am interested in anyone who can identify the make and
} part/model number of its embedded component.
}     (3) If you have also witnessed or possessed any rock, petrified
} wood, prehistoric amber, fossil, coal, meteorite, etc with an embedded
} modern manmade-like component, I am very interested in comparing notes
} with you. Years ago, a spark-plug like component was discovered
} embedded in a geode (Olancha, CA, Feb., 1961).
} 
} If you or anyone else you know of can freely provide these
} contributions, please do so. These requested contributions are
} described in detail on the above webpage.
} 
} Thanks. Please respond. John J. Williams, wizguru@tsc-global.com