Quick Links : Mindat手册 The Rock H. Currier Digital Library Mindat Newsletter [Free Download]

主页关于 Mindat Mindat手册 Mindat的历史版权 Who We Are 联系我们于 Mindat.org刊登广告

捐赠给 Mindat Corporate Sponsorship 赞助板页已赞助的板页在 Mindat刊登广告的广告商于 Mindat.org刊登广告

Learning Center What is a mineral?The most common minerals on earth Information for Educators Mindat Articles The Elements The Rock H. Currier Digital Library Geologic Time

搜索矿物的性质搜索矿物的化学 Advanced Locality Search 随意显示任何一种矿物 Random Locality 使用minID搜索邻近产地 Search Articles 搜索词汇表更多搜索选项

Mindat手册添加新照片 Rate Photos 产区编辑报告 Coordinate Completion Report 添加词汇表项目

Mining Companies 统计会员列表 Mineral Museums Clubs & Organizations 矿物展及活动 The Mindat目录表设备设置 The Mineral Quiz

照片搜索 Photo Galleries Search by Color 今天最新的照片昨天最新的照片用户照片相集过去每日精选照片相集 Photography

Discussions

💬 Home 🔎 Search 📅 Latest

╳Discussions

💬 Home 🔎 Search 📅 Latest

Groups

Recent Images in Discussions

Identity HelpHelp with identification

3rd Apr 2021 19:56 UTCBecky Coulson 🌟 Expert

Hello, I am helping a friend identify minerals for which labels are lost. He has been able to do a streak test (dark grey to black) and has a set of hardness points (it's between 5 and 6). He does not have a locality.

So...not galena, not hematite...skutterudite? Suggestions appreciated. I do not have the mineral, only photos so I am hoping they help.

Many thanks, Becky

3rd Apr 2021 20:00 UTCBecky Coulson 🌟 Expert

Another view

3rd Apr 2021 20:01 UTCBecky Coulson 🌟 Expert

another view - thanks!

3rd Apr 2021 20:47 UTCFrank K. Mazdab 🌟 Manager

Particularly from the last photo showing the uneven front face, it does look like a skutterudite, similar to the Moroccan ones. The hardness also matches. A density determination would additionally help, but it may not be possible (or practical or desired) to remove the specimen from its plastic base. Of course, doing a specific gravity measurement on the whole mass (mineral, base, and glue) might still be worthwhile and would set a lower limit, and may even approach that the mineral if there's a large density difference between the mineral and the plastic (presumably there is) and if also the mineral dominates the overall volume of the pair (maybe somewhat here).

3rd Apr 2021 21:54 UTCBecky Coulson 🌟 Expert

Thank you, Frank. He does has a good electronic balance, so if he has a graduated container we might manage density eventually. He is certainly determined in his efforts!

3rd Apr 2021 22:21 UTCFrank K. Mazdab 🌟 Manager

A graduated container actually isn't necessary, and in fact it's tougher to measure volume precisely than it is to measure mass or weight precisely. Weigh the sample on the electronic balance (W_mineral), then weigh a cup of water on the balance with a sufficient volume of water so later the sample can be fully immersed (W_tare), and then finally weigh the combination of the cup of water with the sample carefully suspended into it with a thin string or hair so it is fully submerged in the water and doesn't touch the bottom (W_suspended).

The specific gravity is the weight of the mineral in air (= W_mineral) divided by the weight of the displaced volume of water (= [W_suspended - W_tare]).

Or fully written out:

W_mineral / (W_suspended - W_tare)

edit: oops... I initially had an extra W_mineral in there, but I think I got it right this time.

4th Apr 2021 07:07 UTCBecky Coulson 🌟 Expert

Thank you, Frank and Keith,

Frank, I forgot about using water with the mineral suspended - thanks!

Becky

4th Apr 2021 08:02 UTCFrank Mersch

The plastic base should not be a real problem: Volume can be calulated easily (V=l x w x h) and density of the poylmer will be 1.2 (PMMA or PC). That gives the mass of the base, too.

Frank

4th Apr 2021 09:10 UTCFrank K. Mazdab 🌟 Manager

good point Frank. Adjusting the combined mineral+base measurements for the mass and volume of the base will require a few extra math steps, but it's certainly not difficult to calculate, and doing so should result in a fairly accurate SG estimate of the mineral.

4th Apr 2021 09:58 UTCFrank Mersch

Mass crystal = Mass Total - Mass base (calculated by measured rectanguar Volume)

Volume crystal = Volume total - Volume base

volume base = height x width x length (all in cm - I am a child of SI)

mass base = volume (in cm3) * 1.2g/cm3

Not that hard ;-)

BR + happy egg hunting

Frank

3rd Apr 2021 21:59 UTCKeith Compton 🌟 Manager

Very much looks like skutterudite from Morocco

Go to top of page