Is this called mint bloom or is it something else? New Pics Added

Icollecteverything · January 29, 2013 10:44AM

braddick · January 29, 2013 10:46AM

I'm going with (partial) grease filled die.

Icollecteverything · January 29, 2013 10:47AM

Now that I see it blown up so large I am thinking it was just a rough planchet that did not get fully struck?

LanceNewmanOCC · January 29, 2013 10:49AM

.
i'll go with strike-through grease
.

dcarr · January 29, 2013 11:23AM

Not struck-trrough grease.

That is sometimes called "starburst" and it is a form of die erosion.
Once the hard surface of the die fails, the erosion progresses in a radial direction.

jedm · January 29, 2013 11:49AM

I wondered about this also, having seen it numerous times on the statehood quarters. There is always something to be learned here. Thanks for a great post.

savoyspecial · January 29, 2013 11:51AM

i think you are confused with what the term 'mint bloom' really means -- it is just a synonym for luster

TomB · January 29, 2013 12:36PM

I would have thought it was due to a partial grease filled die, too, but DC knows this process better than most of us and his explanation of die erosion cannot be ignored. Mint bloom is typically used to describe intact luster.

MsMorrisine · January 29, 2013 12:45PM

What has me puzzled about the die erosion part is that I've seen this on small dollars and the starburst is incuse.

Baley · January 29, 2013 12:47PM

Are the marks raised higher than the fields, or sunk lower? From the pics they look lower, which to me would indicate some kind of struck-through (or post-mint damage such as engraving)

I'm no coiner, but I thought die erosion of that kind would cause raised marks on the resulting coins (unless it was bumpy rust that raised the surface of the die)

braddick · January 29, 2013 10:03PM

<< <i>I would have thought it was due to a partial grease filled die, too, but DC knows this process better than most of us and his explanation of die erosion cannot be ignored. Mint bloom is typically used to describe intact luster. >>

I agree. My confidence level is quickly eroded when a true expert- someone with first hand experience- steps up with a different opinion.

TwoSides2aCoin · January 29, 2013 10:07PM

In some circles it's known as "faux bloom". LOL

PerryHall · January 29, 2013 10:17PM

A coin with extreme die erosion like that is a neat collectable coin---great eductional tool and coversation piece at your next coin club meeting.

Baley · January 29, 2013 11:44PM

Are the marks raised or lowered? <tap tap> "is this thing on?"

roadrunner · January 29, 2013 11:54PM

GW + Rays. Just like the 1853 quarters.

FredWeinberg · January 30, 2013 12:51AM

I'd like to respectfully disagree with the
StarBurst explaination.

In my opinion, it is struck thru grease,
(or some other foreign thin liquid material);
that's the 'look' that such struck-thru's have.

I've examined dozens and dozens of U.S.
Mint Olympic Coin Dies (the cancelled ones)
that have on the Mint Certificate "Starburst"
as the reason for retiring the Die.

None of these 'Starburst Dies' ever had any
disruption on the surface of the die like this Quarter.
Not one of them, and nothing even close visually.

In fact, I usually had a very hard time finding, even
with a strong glass, the very very 'fine' lines on the
Die surface that could be described as 'Starbursts'.

I believe that the viscosity of machinery grease will
leave the effect we see on this States Quarter's surface,
as the coin is struck under 65-75 tons of striking pressure.

Icollecteverything · January 30, 2013 1:17AM

Well........... Maybe this will teach me not to believe what I think I see in a picture. Last night I would have sworn that those "rays" were incuse, like microscopic Grand Canyons. But I figured I better be quiet until I looked at the actual coin again. The whole area appears to be slightly raised! (This week I saw a pic of the reverse of a seated coin here that the eagle appeared to be incuse)

It's still not making total sense to me since I have seen many coins from worn dies that look way different than this. Often the entire design and the fields appear to be mushy and deteriorating. But this one is like a thin layer of the die was pealed away or something and only in the fields around the bust. The rest of the design seems to be fairly sharp. This really does not look like die polishing but could that have something to do with it?

The reason I thought of mint bloom at first was because sometimes on well struck Unc. coins they have a slight aura? or shimmer to them from the high pressure but this is really different.

cladking · January 30, 2013 5:43AM

<< <i>I'd like to respectfully disagree with the
StarBurst explaination.

In my opinion, it is struck thru grease,
(or some other foreign thin liquid material);
that's the 'look' that such struck-thru's have.

I've examined dozens and dozens of U.S.
Mint Olympic Coin Dies (the cancelled ones)
that have on the Mint Certificate "Starburst"
as the reason for retiring the Die.

None of these 'Starburst Dies' ever had any
disruption on the surface of the die like this Quarter.
Not one of them, and nothing even close visually.

In fact, I usually had a very hard time finding, even
with a strong glass, the very very 'fine' lines on the
Die surface that could be described as 'Starbursts'.

I believe that the viscosity of machinery grease will
leave the effect we see on this States Quarter's surface,
as the coin is struck under 65-75 tons of striking pressure. >>

I have neither the experience nor knowledge to comment on this but do agree that the effect
is not consistent with die erosion in my experience. Die erosion has always been most pronounced
around raised die detail and especially the largest such details like the bust because there is no
"back pressure" preventing metal flow into thos areas resulting in more metal flow.

I have to suspect DCarr has some knowledge on this so maybe some dies fail in a specific way
related to movement of the die under stress. Perhaps this is even exascerbated by grease.

dcarr · January 30, 2013 6:44AM

After looking at the 1991-P quarter in the original post of this thread, it is apparent that the "starburst" marks are incuse on the coin, which means that they are raised on the die.
But grease alone is not sufficient to cause that effect. After just a few strikes, under 50 tons of force, any oil or grease would become vaporized and/or dissipated. From some of the president dollars, it is apparent that the pattern grows slowly after numerous strikes, which is not possible from grease alone. I once accidently struck through a piece of rubber. All that was left of the rubber was a wisp of smoke. That particular medal was certainly affected, but had I continued to strike more without cleaning off the dies, the apparent effects of the rubber residue would have quickly diminished.

What I think happens is, with repeated striking, the flow lines on a die become more pronounced. Since the fields of the coin match up to the highest areas of the die, that is where the most stress occurs. This is essentially a form of die erosion and it results in a rougher texture on the die face, especially in the fields. This rougher texture tends to grab onto and hold tiny metal particles, which tend to stick together under that kind of pressure. This gunk looks and feels a lot like grease, but it is mostly fine metal particles. After many repeated strikings, this "gunk" will tend to migrate outward radially.

A die that was retired by the US Mint for "starburst" probably is just a later die state with a rougher texture which tends to retain metal particles. That gunk is probably cleaned off prior to the sale of canceleld dies to collectors.

FredWeinberg · January 30, 2013 7:59AM

Daniel,

If the 'gunk' can be cleaned OFF the Die, then
it wasn't 'IN' the die, leaving a raised area of
a Starburst. It was what we call 'grease', but
could be any type of material similar to it.

As I mentioned, I've never seen a US Mint
Starbust-Retired Die that looked anything
close to what would cause the look of the
Quarter in this post.

Icollecteverything · January 31, 2013 3:54AM

What is up with this 1983 quarter? Is it a weak strike or struck thru grease? I have seen several different quarters that have the hollowed out groove lengthwise thru the bust. (not PMD)

This second 83 quarter appears to be from badly worn and clashed dies.

This 1985 quarter also has the groove thru the bust plus a little hint of the "aura" in the fields in front of the nose and behind the lower hair like the original quarter I posted. It is not as prevalent and it does not start right from the bust and spread like rays.

Is this called mint bloom or is it something else? New Pics Added

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