I really this is an honest question - otherwise you would join my little club of special posters for adding to my frustration. I wrote no such thing. I suggest you forget the word "shiny" when discussing coins as the only coins that are shiny are POLISHED. Proofs are not shiny either. What has been said above is that a $20 has original mint luster over the entire coin. Since most of the die wear that puts the grooves in the die that produces the luster happens in the field starting near the rims, the luster on a coin's relief starts out less reflective (as the die wear starts) because the grooves in the relief part of the die are less developed/pronounced. The entire coin reflects light. I just pulled a baggy, beat up, circulated (XF+), dark gray colored 1991-P Jefferson nickel out of my pocket along with a 2022 BU Lincoln cent and an AU Roosevelt dime that I received in change at lunch. Each of thes coins has luster under my 100W light. The luster on each looks different. Coins have luster! The type of luster collectors need to learn is the original Mint luster on the cent. When the cent gets a little wear on Lincoln's head, that part of the coin will still reflect light (the luster of circulated copper) but it will look differently than the reflection (luster) from the field.
Thanks. That helps me. I am going to look at coins tomorrow so this thread is timely. I'll practice all night.
Never really got it down completely so I took a MS 70 graded gold coin and MS 70 graded silver coin and placed the coin I was reviewing next to them for comparison. If successful in my purchase I will show them in June when we complete the transaction.
Thanks for the caution. I also use the PCGS online photo-grade plus I send pic's to a club senior member and have done well. This tutorial has helped me a lot.
I suggest that you DON'T BUY RAW COINS on the internet or elsewhere anymore. You are not ready yet. PCGS Photograde is a guide. With experience, you will understand what that means. Good Luck.
You are welcome. Just making sure to include something I overlooked. MS-70 is the GRADE of those coins. The amount (full for MS) and quality of their luster is only one part of that grade.
If you have a Proof coin that is super-reflective...probably because of the special Proof Dies....then forgetting about crystalline die structure and/or metal flows....the bottom line is the coins have lots of luster, right ? I don't think you can be a modern proof...be super-reflective...and have BAD luster, right ?
Yes. proofs have lots of luster. BUT in numismatics, "luster" refers to mint frost and not reflectivity. Proofs that are not Matte have mirror reflectivity. A diamond has luster, right? But that type of reflectivity is called "brilliance." Don't get hung up on crystalline die structure . Look at brilliant MS coins and you'll learn all about Mint Luster.
From my days as a metallurgy student, IIRC, all precious metals have a FCC (Face Centered Cubic) crystalline structure, and I really don't think the crystal structure has much to do with the luster of the metal. The texture of the surface is what creates varying luster.
I think the crystalline structure reference was to the die being deformed at the microscopic level when the 100-120 tons of striking pressure were applied...leading to the creation of the ridges. Again, that might just be for Saints.
Plastic deformation doesn't change the crystal structure of the metal. So while I understand your point about die wear creating more vibrant luster due to change in metal flow, the crystal structure still has nothing to do with it.
Plastic deformation is the term used in metallurgy to describe the permanent change in metal after a stress is applied. It has nothing to do with the material types known as plastics. Likewise, crystal structure refers to the repeating spatial arrangement of atoms within a metal. The four metallic crystal structures are SC (Simple Cubic), BCC (Body Centered Cubic), FCC (Face Centered Cubic), and HCP (Hexagonal Close Packed).