The book The First Fossil Hunters claims that the reasons they thought griffins guarded diamonds is because fossilized ceratopsians sometimes have crystals on them and no one knew what dinosaurs were. These fossils were found in the Gobi desert and other dry areas of the area. Sometimes they eroded out of cliffs that were once sand dunes that buried the ceratopsians often standing upright.

@sergpie

Жыл бұрын

That is absolutely fascinating. I’m going to see if I can get that book now haha

Lab-created diamonds are now 60% cheaper than natural diamonds because despite being identical to mined ones, marketing has successfully labeled them inferior.

@Balrog-tf3bg

Жыл бұрын

I’ll just get a lab one and tell my fiancé it’s real when the time comes

@joechang8696

Жыл бұрын

only idiots consider them inferior. it's like paying more for a brand name

@AlmightyRawks

Жыл бұрын

In addition no human lives are lost during dangerous mining operations! I'd say flood it with artificial :) all the way.

@junjunjamore7735

Жыл бұрын

@@Oceanviewgarden That's what the De Beers want you to think.

@aubreejobizzarro1208

Жыл бұрын

I don’t even understand peoples snobbery with lab versus natural. Or the insistence on having flawless natural diamonds. These be the same peeps spending $$$ on “unique” quartz crystals with hydroinclusions in the stones. The only reason to get natural diamonds is because they are imperfect. I specifically buy the lower grade diamonds because they look COOL. They are colored different and have nicks and cracks. They are interesting. I don’t want PERFECT. that’s what the lab ones are for, duhhhh

As a gemstone nerd and mineral collector, thank you for this upload! I would like to share a fun-fact; Blue sapphire is a member of the corundum family, an aluminum oxide that forms a _hexagonal_ crystal structure. We’ll remember this detail. “Sapphire” as a term, originated from Ancient Greek (“sapheiros”, or blue precious stone), which was possibly borrowed from the Semitic “sappir” (ditto), but is hypothesized to be of Sanskrit origin, where the term for the stone is “sanipriya” (dear/cherished by Saturn). Saturn, the _sixth_ planet from the sun, has the unique phenomenon of _hexagonal_ polar storms. In astrology from the Indian subcontinent, the tradition of ascribing Saturnian associations with this specific stone, goes back several thousands of years. 🪐 💎 Thanks again! Be well

@Fireoflearning

Жыл бұрын

Very interesting, thank you!

@attemptedunkindness3632

Жыл бұрын

One of those weird intersections between minerology, etymology, alchemy, and history.

@sergpie

Жыл бұрын

@@attemptedunkindness3632 Indeed. The coincidence(s) in this one left me very intrigued when I first read about it. Those cooky ancients and their serendipitous coincidences lol

@Pixelkip

Жыл бұрын

Thanks for teaching me about my culture :) much love !

@sherishaffertheartistandmy7948

Жыл бұрын

Both the video and this comment are both very interesting, I love it when I learn something new! Thank you to both of you!

The stories about stored and hoarded diamonds are absolutely true, just another way for big business to monopolize the market. Notice how the industry came up with crackpot ideas about buying an engagement ring with the "three times your monthly salary" as a standard starting point. The more you make, the more you spend, how convenient for them.

@Fireoflearning

Жыл бұрын

De Beers did manipulate the supply of diamonds on the market to increase price for many years, although this is no longer the case. Modern prices are actually a more genuine reflection of supply and demand.

@cat-le1hf

Жыл бұрын

that's how you know they're truly worthless.

@vylbird8014

Жыл бұрын

@@Fireoflearning Though De Beers does still have a vital role to play: They run advertising campaigns and coordinate diamond tracking to make sure that artificial diamonds don't displace natural diamonds for jewellery. They are fighting the biggest fear of the diamond trade: A market flooded by synthetic diamonds every bit as good as natural ones.

@76Boomer

Жыл бұрын

Your simplistic vocabulary truly betrays your claim of knowledge

@friskydingo2961

Жыл бұрын

@@76Boomer Your facile lexicon candidly breaks faith in the company of your aver appertaining toward comprehension.🤪

I never understood the popularity of diamonds from an aesthetic point of view. Nothing will ever top the beauty of an opal for me.

There was an empire in South India called the Vijayanagara Empire (founded 1336 according to Wiki), of which it is said that, fist-sized diamonds were being sold by street vendors, meaning it was commonplace and that empire was so wealthy. Funny how diamond and even gold mines have all but disappeared in India.🤔

@Shinzon23

Жыл бұрын

*hail Britania INTENSIFIES*

@rajeevd.296

Жыл бұрын

Yes, and this is said to have happened near what is today Golconda fort. The Nizam of Hyderabad, into the 1900s, still had shoes studded with diamonds and clothes too.

@sergpie

Жыл бұрын

@Alias Fakename To be completely honest; the vast majority of those profiting from the diamonds in Golconda, were, directly or indirectly, local merchants. However, the vast majority of profits were garnered by Jewish, Persian, and Arab diamond traders.

never understood why diamonds are so liked they look like plain cut glass lol, so many other cool gemstones

@vylbird8014

Жыл бұрын

From a distance, yes. Diamonds have a refractive index far higher than any glass, which means they get a lot of internal reflection. In practical terms: They do sparkle. But you can't see it from a photo.

@duetopersonalreasonsaaaaaa

Жыл бұрын

Same. Plus if I did want one for some reason, might as well buy a synthetic one. No need to waste money when you don't need to. Was the diamond industry also the reason why people were told to get the gal an engagement AND a wedding ring? Ughhh such a waste of money, all for a status symbol that won't help you heal from the psychological emptiness causing you to buy things excessively in the first place.

@sergpie

Жыл бұрын

@@duetopersonalreasonsaaaaaa Be a well informed consumer; know what type of Diamond you’re buying (Diamond typology), or go for gemstones that are gorgeous, far cheaper, and orders of magnitude more rare than typical diamonds (spinel, demantoid, zircon, unusually-colored sapphires).

@nosuchthing8

Жыл бұрын

Durable like gold.

@omatsperanta9479

Жыл бұрын

I feel that too

It is a good day when Fire of Learning uploads. Thank you for helping make my smooth brain not so smooth.

It ought to be remembered that there are different kinds of diamonds, and that the vast majority of those on the market (and whose value is more easily controlled by released inventory) are “Type I” diamonds, which are characterized by nitrogen in their crystal lattice. Again, this is the most common form, and the form most inflated in value and manipulated by inventory. Type II (a and b) diamonds are extremely rare, as they are virtually free of any impurities in the crystal lattice, with the exception of Boron being present in Type IIb, which gives the diamond everything from electric conductivity, to colors like pure green and pure blue or violet. The latter are, interestingly enough, what the worlds most famous diamonds have been categorized as. Not that the ancients or our forefathers would’ve known by analysis; but even simply viewing a Type IIa/IIb will make one understand why they were the object of such desire. These are not withstanding the rarity of diamonds colored by unusual chromophores like chromium, uranium, thorium, etc. Of note is that practically all Type II (a and b) diamonds are found virtually flawless or at least internally flawless.

@chillyourself5208

Жыл бұрын

Every colorless lab grown diamond is classified as Type IIa-the purest type of diamond. Less than 2 percent of the world's mined diamonds are pure enough to be classified as Type IIa. Beyond those two points, there is no difference between lab grown and mined diamonds. So are they still rare if they are lab grown? Isnt that artificial rarity as well?

@sergpie

Жыл бұрын

@@chillyourself5208 I think, based on my experience in the retail and wholesale gemstone market, and because this is ultimately a conversation about consumer spending and marketing, that the inherent preferences that the clientele at large have had historically, has dictated over the near two centuries that synthetic gemstones have proliferated in the marketplace, that however identical they may be to their natural, terrestrial analogs, they fail to achieve comparable sell-through irrespective of how cheap they may be. And hitherto; no laboratory has been able to replicate a natural diamond insofar as it is still distinguishable through mere magnification, what is a farce and what is the genuine article, let alone with heat transfer testing. Definitionally, a synthetic diamond is thus not identical whatsoever to a natural diamond. That an object created through the mere chance of an agglomeration of elements and forces through billions of years from beneath our feet, is far more appealing than the product of profiteering from leftover laser crystal development or military technologies that needed to be profited from after the the 1960s contingent to patent expirations. I think, then, that your final question is more rhetorical, as the rarity is very much not artificial. Those that want a diamond, typically will settle only for a diamond as we’ve always understood it; from the earth, predating our meandering artifice.

@monl3807

10 ай бұрын

Get your own channel if you know so much on the subject no o e has the time to read this. 1:05 😅

"How diamonds became desired" *Shiny*

I wonder if other precious gems have similarly surprising histories behind them? Ruby, Emerald, Sapphire, Amethyst, the ultra rare Tanzanite, or the ever common Pearl. This could be your next big subseries! XD

@planescaped

Жыл бұрын

I know pearls have a rich history.

@sergpie

Жыл бұрын

@@planescaped Pliny the elder was the first to correctly identify an emerald as beryl, and compared its green hue to nothing else on earth as far as the serenity he said he’d gain from gazing at one. Emerald in Sanskrit translates to “the green of all living things”. Even the Chinese ascribed the visually pleasing properties to emerald (and beryls) to calm strained eyes. Amethyst means “not drunk”, and became the object of the predilection of Bacchus, as it is the reincarnation of the muse Amethyste, though this story is likely a Victorian-era confabulation, as no mention of it exists accept a brief passage somewhere involving Arachne.

@John081590

Жыл бұрын

Oh they have equally fascinating stories! Pearls for instance are one of the rarest gems in the ancient world. Pearls are formed when an irritant like a parasite or a foreign particle enters the shell of certain sea or freshwater creatures. They envelope the irritant in nacre to protect themselves. Over time the creature just keep building and building the nacre around it until a pearl is formed. Pearls can form on a variety of shelled animals like conchs, abalone, oyster and mussels. Pearls coming from the oyster Pinctada Maxima is the most well known and most people are familiar with. The chances of pearls forming are rare, because it is just by chance that an irritant find it's way into one. But this all changed when the Japanese found a way to deliberately put an irritant in the oyster to form pearls. And thus cultured pearls was born. It made the gem more affordable. However, people who depended on diving for pearls formed naturally (natural pearl) was devastated. Countries like UAE, Bahrain, and Qatar (before they discovered oil) depended on pearl diving for part of their livelihood. It is interesting to know that in the past, these countries had a closely bound relationship with pearls in their culture. Today, cultured pearls are what is most available in the market, mostly coming from oysters(saltwater pearls) and mussels(fresh water pearls). To this day, naturally formed pearls still command a very high price compared to their cultured counterparts. In addition to that, pearls coming from creatures like abalone, conch, and the melo-melo pearl coming from a type of gastropod still remains extremely rare and very expensive as attempt to culture them are relatively unsuccessful. They look way different from the pearls we are familiar with and they are absolutely stunning in their own right.

@nunyabiznes33

Жыл бұрын

Pearls only became "common" when the technology to seed them was developed.

@sergpie

Жыл бұрын

@@nunyabiznes33 If one goes to Iraq (Basra, specifically) there is still a small but active pearl industry, where virtually none of the pearls are seeded. Same in Burma but in much smaller scale. Absolutely beautiful pearls when the nacre is well-formed, but so damned expensive; I was party to the sale of a few loose Iraqi pearls of good quality, and they retailed for about $2800 each. I can only imagine what a strand must go for.

We just love shiny stuff, don’t we

@playgirl7305

Жыл бұрын

Yes, just like the animals which stand in the middle of the road at night and are 'fascinated' by 2 shiny spots coming towards them.

Emeralds, opals, and ruby's are so much more beautiful and rare than diamonds. Diamond value is a result of marketing.

I opted for a simple wedding band when I got married. I didn't even want an engagement ring. I love how diamonds sparkle, but I'm OK without them.

As always, both informative and entertaining.

I think the big reason they became expensive is because somehow the public got convinced that engagement rings are supposed to have a diamond on them. I wish the how and when of that had been discussed.

@johnhanley9946

Жыл бұрын

He did mention that DeBeers began the trend in the 1940's with the advertising slogan, "A Diamond is Forever".14:57

@exposingtruth600

Жыл бұрын

The most I’ve seen discussed on this topic is from some show on some old tv program called “Adam ruins everything”

Scarcity / Value 101 "Look what I have." "Hey, that's cool. Are there more of them?" "Yes, but they are rare and difficult to come by." "Oh, it's valuable then."

You did your joke so well - such deadpan delivery!

Excellent video as always!

The fact that the Hope Diamond used to be at least 3x larger makes me mad

@electric_crickets

Жыл бұрын

Lulz. Reeeeeee

@sergpie

Жыл бұрын

The vast majority of high quality gems are about 5-20% of the original rough size. It would’ve been nice to know the quality of the rough, as, being a Type IIb Diamond, the hope rough would likely have been entirely flawless or internally flawless. These types of diamonds have a paradoxical size/clarity relationship

Love your channel !

I like the idea of synthetic gems. Less likely that they'd fund conflict.

@nunyabiznes33

Жыл бұрын

@@DG-iw3yw yes that too. Though I don't know how destructive sourcing the raw materials for synthetics would be, that's why I didn't mentioned it. Diamonds at least just require carbon, saw a vid of a company that make them out of hair. 💇‍♀️✨💎

@sergpie

Жыл бұрын

@@nunyabiznes33 There’s a company called lifegem that will cremate and pressurize your loved ones into a Diamond.

Very interesting and informative! 💎

Very interesting history of diamonds. Thanks

Thank you for your hard work on this. But let us not forget that ancient Egyptians also revered the diamond for its spiritual purity. Cheer!

Fascinating; I knew Gryphons were associated with guarding treasure for the Greeks and Roman's, but I didn't know they were also thought to guard Indian diamonds.

Hey can u re-upload the usa part 2 again btw love the way u explain historical topics.

Great video! Thank you.

I've noticed actual commercials lately pimping diamonds like they're some kind of wholesome commodity. GF'd diamond industry... seriously!? XD

I just love the "however".

Better gems available for a fraction of the price. Red Spinal and fancy Yellow Topaz are two of my favourites.

I like diamonds but since I work so much with my hands, I couldn’t trust myself with a diamond engagement ring. Plus, not everyone thinks about the upkeep. To protect the stones and metal, and SETTINGS, if you wear your engagement ring frequently, you should have it cleaned frequently and the settings tightened. While it isn’t ridiculously expensive, adding jewelry cleaning and repair to a list of chores sounds like a pain. I really like the idea of an engagement ring+ a simpler wedding band. The engagement ring worn for special occasions or dressing up, and the wedding band for everyday wear and tear. As far as diamonds go; I know you peeps spend $$$ on “unique” quartz crystals with hydroinclusions in the stone. Why on earth are you insisting on natural flawless diamonds? And don’t get me started on how the market has now marketed “yellow” diamonds when they were considered undesirable 20 years ago…. Same with “chocolate diamonds”. I think diamonds with flaws are honestly super cool. I like the discoloration and the inclusions on them. It reminds me it is a pretty stone that came out of the earth, and doesn’t look like some cheap cut crystal or glass. It just seems counter intuitive if you want “naturally flawless”. That’s an oxymoron!

I've read that the Argyle Diamond Mine in the Kimberley region of northern Western Australia has brown diamonds in addition to the pink and clear diamonds. They named the brown ones: Champagne and Cognac depending on their shade.

@neilchisholm8376

Жыл бұрын

How do you know that they are diamonds and not topaz. To the man in the street without scientific analysis they would look the same. You just have to take the merchants word for it.

@sergpie

Жыл бұрын

@@neilchisholm8376 Refractivity, scintillation, and scratch-test.

Marketing the “oh, shiny” feeling with a worthless rock that can be made in a lab.

I recall reading of the meat-in-the-snake-valley method serving as a major plot point in one of the tales of Sinbad. The 1001 nights really was attempting to gather stories from all over the world.

I came here because of the community post lol and I dont regret it :D

Great video 👍

The price & popularity of diamonds, in part, was created by a clever marketing ploy. DeBeers bought most of the mines that produced the high-quality diamonds. Then? The slogan, "A diamond is forever" along with hiring beautiful, popular cinema stars as spokeswomen, that clinched it. The codfish lays thousands of eggs, the hen lays only one. The codfish never cackles to announce what she has done. Codfish are mostly unknown while the hen, we prize. Proving to the world, it pays to advertise. (I didn't write this; I do think it's funny as well as having a "ring" of truth to it.)

How did people prior to scientific analysis know the difference between, for example a blue diamond and a sapphire? Both are prized but diamonds are more so. Similarly, for diamonds of a red hue, how were they differentiated from Rubies or even garnets? Did you have to trust the merchant selling the gems or where there ways to identify pure carbon diamonds with impurities that gave other colours. Even today, without chemical analysis, you can’t be sure what you are purchasing. For example how did they know the Hope Diamond was a diamond and not a sapphire?

Wouldn't it be probable that an international cartel formed, replicating the artificial scarcity of diamonds that De Beers once used?

Missing the History of... series! Justin, hope you are well and hope you return to that series soon! 🙏

My mom has a 6carats diamond ring and 10carats pendant, we just noticed that it sparkle less that her other diamonds. Our jeweler advised to have it refaceted as it’s an old cut or he also mentioned about candle light I’m sure, but the carat will be lowered from the original size. Should we have them refaceted or keep it that way?

the things we as humans choose to put value on never ceases to amaze me. ripping up land and exploiting people...for a rock

I can't believe there are no comments about Steven universe here.

You should do a “History of Tartaria” documentary about the mud flood theory of the past. Interesting stuff

How did they made cut of diamond in these times of yore? What tool could cut a substance of such hardness??

This video is a diamond in the rough in terms of talking about diamonds, at least for me

Random thought: what if gems were lucifer's radiance that were shattered and scattered when he was cast out of heaven but fell to earth instead of hell?! lol i may just be high.

Shine bright like a diamond you wild capybara man!

Good video

So many still diamonds out of Africa and parts of East India and never give these people credit while taking their minerals but there's a reaping and sewing hell awaits for all that you took for greed 🤦🏻‍♀️😳📽️📺✨

No where near or rarest but indicated by our olds,,first depicted Gem of value, we know better now...they are Beautiful indeed.

I've read that the only material hard enough to cut a diamond is a cut diamond. So how was the first diamond cut?

@vylbird8014

Жыл бұрын

The only material hard enough to /scratch/ a diamond is another diamond. Cutting is another matter entirely. They shear along the crystal plane: A precisely placed chisel and a good whack from a hammer and it just splits in a perfectly flat plane at the perfect angle. If the gemcutter knows how to do it right.

@franl155

Жыл бұрын

@@vylbird8014 - thanks!

@electropainted

Жыл бұрын

@@vylbird8014 same question I had. thanks, good to know!

@vylbird8014

Жыл бұрын

@@electropainted It also means that the gemcutter is staking the value of the diamond upon knowing exactly where to position that chisel and how hard to hit it. A mistake can be expensive.

Nice

I loved watching the blood diamond movie

Thanks!

@Fireoflearning

Жыл бұрын

Thank you!

Whatsup my dude

Love these vedios you should do a documentary of Russia

Dutch: "Here. I found these diamonds in Brazil. Pretty cool, huh?" Europeans: "Ew. Disgusting. Get this filthy, clearly inferior diamond away from me" Dutch" *takes the Brazilian diamonds on a trip to India" Europeans: "Mon dieu! What a beauty!"

@sergpie

Жыл бұрын

Plot-twist; Brazil has been the locale of the largest red Diamond ever uncovered, and it was done by a farmer tilling his field. Another treat are Brazilian emeralds, copper-bearing tourmalines (paraiba), and vivid blue (Santa Maria/Maxixe) aquamarines.

I'm personally more attracted to emeralds or rubies. Diamonds are just too plain for me.

@martinvanburen4578

Жыл бұрын

always a contrarian

@applegal3058

Жыл бұрын

@@martinvanburen4578 haha, of course 😄

Small clear diamonds are common or the diamond industry couldn't exist the way it dose today but larger clear and flawless diamonds are rarer and rarer still are coloured diamonds though if you ask me the queen of gemstones is opal.

@sergpie

Жыл бұрын

What I love about opal, is that the majority of it, was likely a tree or some residue of some living critters squished and layered with silica and other elements.

We still have a very close cognate to the Greek adamos, “adamantine”, which means diamond-like. Placer ryhmes with plaster.

Volcano: "MAKE IT RAIN"

Just for your information the Greek word adamas (αδάμας) does not mean unbreakable but untameable.

This manipulation of prices of diamonds by DeBeers is interesting to me, since Blanchard and Company brought suit against people who were keeping the price of gold artificially low.

Have you done (or will you do) videos about others gems or jewlery items like garnets, amethysts or pearls?

I've never understood the appeal of jewelry or diamonds. But if it's something you feel like you need to wear, all the luck to you...

Could you do a documentary about Mali or one of the medieval African kingdoms that existed at the time ? Or a history of the Muslim caliphates would be very cool as well or maybe just the rashidun caliphate

Was there a Pink Floyd sound-alike?

Literally a rock

Funny train of thought; I just imagined us nuking an astroid to avoid a collision with it, and end up with diamonds raining down on us. What would that do to the market?

@theobserver9131

Жыл бұрын

They would probably be radioactive, and we would end up using them as self charging batteries.

@sergpie

Жыл бұрын

Kinda related; there is a form of zircon known as “metamict”, whose crystal structure has, through millions/billions of years, been rendered completely amorphous, but it loses none of its physical properties (hardness, tenacity, fracture, refractivity). This loss of structure is due to thorium and/uranium present in the crystal lattice, and usually exhibits shades from brown to vivid green. If of high quality, they are truly beautiful and unique when cut. In the sciences, these zircons have been dated as being some of the oldest crystals on earth. Though radioactive, they are in such small activity that they are perfectly safe to wear.

So when's your next Michaelmas video?

The one thing that diamonds are not is rare. Cubic Zirconia is not meant to look similar to diamonds but to the natural stone zircon. Now the thing with diamonds is making a perfect Diamond from growth. Taking a side of the diamond and making a 100 percent diamond of excellent diamonds, at a fraction of the price.

A huge number of diamonds in circulation are blood diamonds, especially South African

Why would you cut the biggest diamond ever into pieces 😭 just polish it

It's easy to find diamonds, just dig straight down!

@vylbird8014

Жыл бұрын

Never dig straight down!

@I.V.G

Жыл бұрын

@@vylbird8014People still do, even to this day!

Moissanite is the best alternative to diamonds in case anyone was wondering

since we never dug past the 8km(or mile i forget) and we just basically guess the earth has a mantle, crust, and core...i mean we have literallly no idea what our earth is made of. so crazy how someone can see a diamond and think ooooohhhhh i need that haha. but we are weird creatures. i mean industrial use for diamonds seems more plausible for future progression..but telling the market theyre basically useless aside to be used on cutting machines and stuff would literally cause the crash of the world haha

Diamond are forever so are plastic bags 🍻

So they were valued because they were "unbreakable"? If you can't cut them, they're not very pretty. But the symbolism of unscratchable is powerful. Even now, on engagement rings, the symbolism is "forever" "unbreakable". In medieval times, natural diamond points would be set into rings, a point that can scratch anything. A symbol of power perhaps?

3:15 Sadly diamonds don't cure niegherness lol

15:16 39!!!

Gold I understand, diamonds I do not

it's funny, the Hope Diamond is worth a fraction of minecraft xD

brandenburg 4 💚💚

That thumb nail looks like Dustin Diamonds....

Lord Chrisna always wore diamonds

Even if I was loaded.....I would NEVER purchase any gem stones, unless they are created in the laboratory. Diamond mine workers are treated no better than slaves & the mines destroy the environment. Far past time to do away with the diamond industry, unless they are lab created! 🤨

So, when/how did diamonds become a girl's best friend? btw: "...not set in stone." -😄😄😄nice.

Please increase the volume of your background music or remove it. The level it’s at in the video is so distracting as it’s barely audible and forces you to focus on it to try to determine if it’s from your video or some other external source.

"...just joking..." Lol

I guess the Greek word for Atom is related to their word for diamonds… interesting. 🤔Unbreakable=💎 =☢️…😊

Don't man-made diamonds lumines under a blacklight and that is how to can tell them apart from naturally formed diamonds?

😎

@egaglemaster6348

Жыл бұрын

Ur first

Can we eat Diamonds? Or Gems in General?

You gonna make part 2 of history of the United States or not?

@Fireoflearning

Жыл бұрын

Unfortunately not likely any time soon

At one point in the late 20th century, geologists theorized that vast quantities of diamonds were available off the South African coast. De Beers shut down this exploration, for fear of crashing diamond prices. kzread.info/dash/bejne/iJphlrmLmK2cops.html

IT RAINS DIAMONDS ON OTHER PLANETS

Don't dig str8 down

How did they know they were diamonds before there were plate glass windows or mirrors to scratch? 🤣

@phoenixkali

Жыл бұрын

I guess they used it as a gramophone needle or end of a jackhammer