How Much Gold is Hidden in Your Rock? Specific Gravity Testing in Hill End
How Much Gold is Hidden in Your Rock? Specific Gravity Testing in Hill End
When you’re out metal detecting in a legendary goldfield like Hill End, the dream is always that loud, clear signal that leads to a beautiful gold specimen. But once you have that quartz and gold rock in your hand, the big question remains: How much actual gold is locked inside?
In our latest adventure, Nick from Picket Prospecting joined us to demonstrate exactly how to answer that question without crushing the rock and losing its beauty.
The Hill End Experience
We spent the day swinging the Minelab SDC 2300 [04:04]. Hill End is famous for its specimen gold—just weeks prior, someone found a massive 1.34 oz piece! While we spent a good portion of the day digging up old nails and aluminum trash [14:56], the persistence paid off. Nick managed to spot a stunning pink-stained quartz specimen right on the surface [07:03].
What is a Specific Gravity Test?
If you want to know the gold content of a specimen but want to keep the rock intact, you use a Specific Gravity (SG) test. This physics-based method uses the known density of gold versus the density of host rocks (like quartz) to calculate the weight of the metal inside.
What You’ll Need:
- A digital scale [16:35]
- A container of water
- Thin string (pre-wet so it doesn't absorb water during the test) [18:21]
- A "bridge" to hold the scale over the water (Nick used a broken fan blade!) [16:46]
The Step-by-Step Process
- Get the Dry Weight: Weigh your specimen normally on the scale. Nick’s find came in at 5.46g [17:51].
- Get the Wet Weight: Suspend the specimen from the scale using the string so it is completely submerged in water but not touching the bottom or sides [18:52]. This gives you the displaced weight. Nick’s wet weight was 4.32g [19:03].
- Run the Math: There are a few formulas you can use. Nick prefers an "old-timer" method that accounts for different mathematical constants [20:06].
The Results
After running the numbers, the calculation showed approximately 2.3 grams of gold hidden inside that 5.46g rock [21:13]. That is a fantastic ratio for a specimen!
Safety Tip: Don't Get Zapped!
While we were out there, the weather took a turn. If you’re metal detecting and a storm rolls in, take cover. When lightning is nearby, your detector might start "screaming" or behaving erratically due to the electrical interference [09:22]. We had to drop the gear and hide under trees until it passed—gold is great, but safety always comes first!
Watch the full video below to see the exact formulas Nick uses and to see the beautiful Hill End scenery!
Watch: How Much Gold is Inside? Specific Gravity Test in Hill End