A 73 carat rough stone (Stone A) submitted for identification. Stone A labeled as “Berlian” (Diamond in Malay language) by the customer, and were told mined from East Malaysia, Borneo Island Sabah based on the information provided by the customer’s supplier. Customer has strong believe that the submitted stone is a diamond base on the two identification test method performed by the supplier in front of the customer.
The customer further shared with us 2 mobile recorded videos during the unique “identification” test performed by the supplier. – Please take note that we only take screenshot from customer videos as reference, no actual video attached in this note.
The first video, Test 1, a person using a hammer to knock on the Stone A multiple times, and no visible break on the stone base on the person voice in the video. The customer were informed that the Stone A is the hardest mineral on earth, a diamond, hence will not break under intense knocking.
Second video, the Test 2, showing that the Stone A drawing a straight line on a glass-like material repeatedly in one direction until the material broke into two pieces. The intention of the video is to convince the customer that diamond is commonly used for cutting glass, and the Stone A able to “cut” the glass because it is a “diamond”.
Customer want us to test and confirm the Stone A is a Diamond.
A standard gemological testing were performed by us. Under microscope, multiple hexagonal crystal structure inclusions were easily found in the stone. Obvious surface cracks were also found (can be seen on the bottom left of Image A), possible due to the seller’s Test 1, the hammer knock, which cause this surface cracks. We further measure the refractive index of Stone A with standard refractometer, and the RI result obtained is 1.54-1.55 which ruled out the possibility of a diamond which has OTL under standard refractometer. Stone A’s SG measured with the result of 2.66, Diamond will have SG of 3.52. Under standard polariscope, we found bull’s-eye optical figure in the Stone A, the bull’s-eye is a special type of uniaxial figure that’s displayed only by the mineral quartz. Further test with IR, and the obtained graph matched with quartz’s IR fingerprint spectrum. With all the information and result gathered, we issued the report for the customer that the testing article Stone A is a Rock Crystal, a variety species of Quartz.
As in the Test 1 video, the supplier’s “diamond identification” method is not recommended, and it is a destructive test. No doubt diamond is the hardness natural mineral so far found on earth, but one should understand that mineral hardness is measured base on the mineral scratch resistance, and not a toughness measurement. Hammer is definitely a lot tougher that diamond. Besides, diamond has four cleavage direction in mineral structure, if diamond receives a sharp blow right in one of these directions, it can easily cleave, or split into multiple pieces.
Many glass cutting tools are coated with diamond due to diamond has highest mineral hardness of 10 which can scratch on any mineral same hardness or lower than 10. Quartz has mineral hardness of 7, and most of the glass hardness is lower at around 5 to 6, which why in the Test 2 video, we can see the Stone A able to scratch the glass, and in the end “cut” the glass into 2 pieces.
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