Question

glassy , used to make glass , no cleavage planes​

Answer 1

Answer:

Explanation: MINERAL NAME LUSTER (appearance) HARDNESS DISTINGUISHING PROPERTIES

Pyrite Metallic Slightly harder than glass Hardness greater than glass (H ~ 6-6.5); Brassy yellow color; black streak; Crystals commonly cubic; no cleavage.

Galena Metallic Softer than glass 3 perfect cleavages at 90 degrees, high density.

Answer 2

Quartz is the material which is glassy, used to make glass and has no cleavage planes.

Why is quartz glassy:

Since quartz is hard, crystalline mineral mainly composed of silica (silicon dioxide), it exhibits glass properties.

Properties of quartz includes,

• It is the only stable polymorph of crystalline silica produced on the Earth‘s surface. It can be found in all forms of rocks such as igneous, metamorphic and  sedimentary.

• Quartz glass is also an   extremely versatile material and used in various materials. It possess excellent thermal properties, optical transmission, good electrical and corrosion performance.
• Quartz differs from glass in its 99% silicon dioxide content and its symmetrical arrangement of molecules.

Natural quartz  is very rarely used in the industry as it contains several impurities which increases the cost of extraction.  The most commonly used raw material is "cultured quartz",   which is the quartz crystals which are grown in  controlled conditions. Examples of quartz colours: golden yellow, rose, smoke and purple.