（1） Natural sulfur
Natural sulfur refers to the orthorhombic crystal system α Sulfur. The molecular formula is S, and the theoretical sulfur content is 100%. In addition, natural sulfur usually contains some impurities. Natural sulfur in volcanic rocks often contains small amounts of arsenic, tellurium, selenium, and titanium, while sedimentary natural sulfur often contains impurities such as calcite, clay, organic matter, and asphalt.
Natural elemental sulfur is generally needle shaped and plate-like crystals, often produced in irregular blocks. The crystal shape is rare and usually appears in dense blocks, powder like, granular, strip like, and film like forms.
Natural sulfur is light yellow or brownish yellow, with colors ranging from red, green, gray, and black when impurities are present. The Mohs hardness is 1-2, and the specific gravity is 2.05-2.08; Embrittlement, incomplete cleavage, shell like fracture surface, weak conductivity and heat transfer. The stripes are white yellow white, transparent semi transparent, resin diamond luster; When burning, it emits a blue flame with a pungent smell of sulfur. Corrosion resistance. Under conditions of 360 ℃ and higher temperatures, sulfur strongly interacts with oxygen to form sulfur dioxide. At around 400 ℃, sulfur reacts with hydrogen to form hydrogen sulfide. As the temperature continues to rise, it dissociates and completely decomposes into water and sulfur at 1690 ℃. Sulfur and caustic alkali are heated together with ammonia solution to form polysulfides or thiosulfate. Sulfur is insoluble in water and more soluble in organic solvents and carbon disulfide. Sulfur appears as an oxidizing and reducing agent and is a chemically active element.
（2） Pyrite
Pyrite, also known as pyrite, has a molecular formula of FeS2, with a theoretical sulfur content of 53.45% and an iron theoretical content of 46.55%. The pyrite produced in nature often contains various metal elements such as cobalt, nickel, arsenic, selenium, antimony, copper, silver, and gold. Some sulfides can also contain very trace amounts of rare elements such as tellurium and germanium.
Pyrite belongs to the equiaxed crystal system, with common crystal forms being cubic and pentagonal dodecahedral.
The color of pyrite is mostly light brass, with a surface often brownish or yellowish brown. Fine powdery pyrite aggregates are often green black in color. Hardness is 6.0-6.5, specific gravity is 4.9-5.2. Fragile in nature, with streaks of brown black or green black. Strong metallic luster, opaque, with weak conductivity. It has thermoelectric properties, and some variants have detection properties, with uneven fracture surfaces and occasional shell like fractures.
（3） White iron ore
White iron ore (FeS2) is the same as pyrite, and both belong to a homogeneous binary complex, which is a rhombic crystal system, and the crystals are often produced in a plate-like shape. The aggregation is in the form of nodules, spheres, stalactites, and shells.
White iron ore is a light brass color with a slight gray or light green hue. The fresh surface is approximately tin white, with dark gray green stripes and a metallic luster. Opaque, with a hardness of 5.0-6.0 and a specific gravity of 4.6-4.9, brittle in nature, incomplete cleavage, and uneven fracture surfaces with weak electrical properties.
（4） Magnetite
Pyrrhotite [Fe1-xS] is two types of homogeneous polymorphs, hexagonal or monoclinic, often appearing as dense granular blocks with few crystals and plate-like crystal shapes.
The fresh surface of pyrrhotite is antique copper brown, with a surface often dark brown or dark brown, opaque. Metallic luster. The stripes are grayish black. Hardness 4, brittleness, specific gravity 4.58-4.70. Magnetic, but with varying strength. Has conductivity, and the fracture surface is uneven to shell like.