PERTEMUAN KE II: PERTEMUAN KE II: SIFAT FISIK MINERALSIFAT FISIK MINERAL

MODUL 2MODUL 2

IDENTIFIKASI MINERALIDENTIFIKASI MINERAL

WarnaWarnaBentuk KristalBentuk KristalCeratCeratKilapKilapKekerasanKekerasanBelahan dan PecahanBelahan dan PecahanSifat lainSifat lain

Warna Warna

Streak (Cerat)Streak (Cerat) Black - Graphite Black - Graphite Black - Pryite Black - Pryite Black - Magnetite Black - Magnetite Black - Chalcopyrite Black - Chalcopyrite Gray - Galena Gray - Galena Limonite - Yellow-Limonite - Yellow-

brown brown Hematite - Red-brown Hematite - Red-brown

LUSTERLUSTER (KILAP): (KILAP):refleksi mineral dalam menangkap sinar: refleksi mineral dalam menangkap sinar:

ada dua yaitu metalik dan non-metalikada dua yaitu metalik dan non-metalik

Non metalik: kilap kaca, tanah (earthy) dan tidak memantulkan sinar (dull)

Cleavage (Belahan)Cleavage (Belahan)

Mengikuti Mengikuti bentuk bentuk kristalkristal

Fracture (Pecahan)Fracture (Pecahan) Yaitu bentuk permukaan Yaitu bentuk permukaan

antar atom penyusun antar atom penyusun mineral saat mineral mineral saat mineral pecah atau hancurpecah atau hancur

Pecahan: Pecahan: beraturan (regular) beraturan (regular) tidak beraturan tidak beraturan

(irregular)(irregular) Permukaan pecahan: Permukaan pecahan:

Kasar (splinterry) Kasar (splinterry) Halus (smooth)Halus (smooth) berbentuk kurva berbentuk kurva

(conchoidal): seperti (conchoidal): seperti gelas saat pecah. gelas saat pecah.

Kekerasan Kekerasan

Crystal Shape Crystal Shape (Bentuk Kristal)(Bentuk Kristal)

KubikKubikPrismatikPrismatikTabular Tabular

(berlembar)(berlembar)MenjarumMenjarumHexagonalHexagonalPiritohedronPiritohedron

Sifat LainSifat Lain

MagnetismMagnetism - A few minerals are - A few minerals are attracted to a magnet or are themselves attracted to a magnet or are themselves capable of acting as magnets (the most capable of acting as magnets (the most common magnetic mineral is common magnetic mineral is magnetite). Because these are so rare, magnetite). Because these are so rare, this property helps narrow the this property helps narrow the possibilities drastically when trying to possibilities drastically when trying to identify an unknown specimen. identify an unknown specimen.

FeelFeel - Some minerals, notably talc and - Some minerals, notably talc and graphite, feel greasy or slippery when graphite, feel greasy or slippery when you rub your fingers over them. The you rub your fingers over them. The greasiness occurs because bonds are greasiness occurs because bonds are so weak in one direction that your finger so weak in one direction that your finger pressure alone is enough to break them pressure alone is enough to break them and to slide planes of atoms past and to slide planes of atoms past neighboring atomic layers neighboring atomic layers

Taste Taste - Geologists use as many - Geologists use as many senses as possible in describing and senses as possible in describing and identifying minerals. Taste is one of identifying minerals. Taste is one of the last tests to be conducted, the last tests to be conducted, because some minerals are because some minerals are poisonous. Some minerals taste salty-poisonous. Some minerals taste salty-most notably halite (salt). Sylvite, a most notably halite (salt). Sylvite, a mineral similar in all other properties to mineral similar in all other properties to halite, tastes bitter. Taste is thus a halite, tastes bitter. Taste is thus a diagnostic property because it diagnostic property because it distinguishes between these minerals. distinguishes between these minerals. NEVER TASTE A MINERAL UNLESS NEVER TASTE A MINERAL UNLESS INSTRUCTED TO! INSTRUCTED TO!

Reaction with Dilute Hydrochloric Reaction with Dilute Hydrochloric Acid Acid - This is actually a chemical - This is actually a chemical property rather than a physical property rather than a physical attribute of a mineral. Minerals attribute of a mineral. Minerals containing the carbonate anion containing the carbonate anion (C03)2- effervesce ("fizz") when a drop (C03)2- effervesce ("fizz") when a drop of dilute hydrochloric acid is placed on of dilute hydrochloric acid is placed on them. Carbon dioxide is liberated from them. Carbon dioxide is liberated from the mineral and bubbles out through the mineral and bubbles out through the acid, creating the fizz. This test is the acid, creating the fizz. This test is best performed on powdered minerals. best performed on powdered minerals. Calcite (calcium carbonate) will Calcite (calcium carbonate) will effervesce readily in either massive or effervesce readily in either massive or powdered form, but dolomite (calcium-powdered form, but dolomite (calcium-magnesium carbonate) reacts best as magnesium carbonate) reacts best as a powder. a powder.